What Exactly Does Mexico Export to the US?

One of the many ways conventional economic theory hinders our discussions of trade is it gets us thinking about goods “produced” in one country and “consumed” in another. Mexicans grow tomatoes, drill oil, sew shirts, and assemble cars; Americans eat, burn, wear and drive them.

Most trade in the real world does not look like this. What you have, rather, are commodity chains, where different parts of the production process take place in different countries. In most cross-border transactions, the buyers are not consumers, or even distributors, but producers who use the imported goods as inputs. And in many cases, the relevant transactions are not arm’s-length market exchanges, but transfers within a single corporate structure. Even the final purchasers may not be consumers: In general, investment goods and exports have higher imported content than consumption goods do.

Case in point: US-Mexico trade. What with the latest eruption from DC, I was curious what US imports from Mexico actually look like. [1] Here’s what the Census says:

$ millions % of total
Consumer goods 84,572 26.6
   food 22,432 7.0
   autos 23,434 7.4
   clothing 5,257 1.7
   others 33,448 10.5
Industrial inputs 89,583 28.1
   oil 13,689 4.3
   other raw materials 7,568 2.4
   auto parts 53,175 16.7
   other intermediate goods 15,152 4.8
Investment goods 113,312 35.6
   computers 41,778 13.1
   vehicles 31,943 10.0
   other machinery/equipment 39,590 12.4
Services and other 30,872 9.7
Total 318,338 100

As you can see, consumer goods account for only about a quarter of US imports from Mexico. Given that a large fraction of the service imports are tourism, the total share of consumption in US imports from Mexico will be a bit higher, between 30 and 35 percent. [2] (But presumably tourism would not be affected by a tariff.) The remainder is divided about evenly between industrial inputs (raw materials plus intermediate goods like cloth, steel, auto parts, etc.) and investment goods. Machinery and equipment, including computers, account for an impressive 25 percent of Mexican exports to the US. Petroleum products, despite the widespread perception of Mexico as an oil exporter, account for less than 5 percent.

OK, so why does this matter?

Well, it’s enough, to begin with, that most of us have a distorted idea of what “trade” involves. It’s always dangerous to talk about something at a high level of abstraction without a clear sense of the concrete reality involved — even if, in a given case, the abstract description works fine.

But in this case I don’t think it works fine. I think our model of one country and producing and the other consuming, misleads us in some important ways about the likely impact of something like Trump’s tariff.

First of all, the fact that trade is normally part of a longer commodity chain helps explain why trade flows are often insensitive to changes in relative prices. Notice, for instance, the $50 billion auto parts imported from Mexico — about one-seventh of total Mexican exports to the US. Some of these parts may be generic but most presumably represent investment by the parent company in a specialized supply chain. There’s little or no short-run possibility of substituting components from elsewhere in response to changes in relative prices. In any case, insofar as the importer and exporter are part of the same corporate structure, the relevant price is an administered one that presumably has more to do with internal accounting practices than with exchange rates, tariffs or other macro phenomena. This kind of trade is the excluded category in orthodox trade theory — it doesn’t responds rapidly to changes in prices, but neither does it reflect any fundamental differences in natural resources or other “endowments” between countries.

The second reason the composition of trade matters is when we look at the distributional impact. If Mexican exports were just corn tortillas, as some people seem to imagine, it would be relatively easy to answer “who pays” for a tariff. You just estimate the price elasticities of supply and demand and do the math. (OK, maybe not that easy.) But with a high proportion of intermediate and investment goods it’s much trickier. Especially since there are profits collected at a number of points along the commodity chain, so an increase in the price of Mexican imports at the border is not necessarily passed on to ultimate consumers. Some fraction will presumably come out of the various rents along the way. Even the broad claim that it must ultimately be Americans who pay doesn’t hold, since a large fraction of imports are inputs for export industries.

The third reason follows directly. Insofar as the final users of imports are exporters, tariffs and other relative-price changes will have less of an effect on the trade balance. In the old days of import-substitution industrialization people took this problem seriously — they recognized that the effective rate of protection  for a given industry might be quite different from the statutory rate, depending on how dependent the industry was on imported inputs. In this case, if a large fraction of Mexican imports are destined for US export industries — and they are — then a tariff on Mexican goods will improve US competitiveness less than the textbook analysis would predict.

Finally,  the disproportionately large share of intermediate and investment goods in international  trade should factor into how we think about trade in general. The more I study this stuff, the more I get the sense of international trade and finance as a world unto itself — sitting on top of, dependent on, the rest of the economy, but irrelevant to most of the routine activity of extracting human labor to meet human needs. Imports are purchased to make exports, which will be purchased to make more exports to somewhere else.

An exaggeration? Yes, but maybe not an extreme one. Somewhere in Civilization and Capitalism, Fernand Braudel describes the early modern world as an archipelago of towns scattered around the margins of an interior world — whether in France or India — that remained focused on immediate, local needs. The boundary regions were more connected to each other than to their own hinterlands perhaps only a few miles away. Mutatis mutandis (and there’s a lot of mutatis!) I think something like this applies today. Traders and producers for trade are mostly much more integrated with each other than with the rest of us. Your t-shirt is a valid counterexample, but not necessarily a representative one.

In summary: Most US imports from Mexico are intermediate and investment goods, not consumer goods. A tariff on Mexican goods is more likely to raise costs for US businesses — including for US exporters — than to lead people to substitute American-made goods for Mexican ones.


[1] This is my own categorization of the more detailed breakdown given by the census. I’ve included computers with investment goods because most computer expenditure in the US is by businesses, not households. Yes, some computers are purchased by households, but on the other hand some autos are purchased by businesses, so it probably balances out.

[2] Under the conventions of the national accounts, when someone from country A visits country B as a tourist, their spending there counts as a service export from country B to A.



UPDATE: I feel obliged to point out that I anticipated the latest iteration of “Mexico will pay for the wall’ towards the end of this post from last summer.

UPDATE 2: As Peter K. points out in comments, my line about trade within corporate supply chains not responding to relative costs doesn’t really make sense as written. As he reasonably asks, in that case why would they relocate production to lower-cost areas in the first place? What I should have said is that intra-corporate trade (1) isn’t responsive to *short-run* changes in relative prices and (2) is responsive to long-run changes, but on the supply side, not the demand side. I.e. if there were a large persistent rise in prices in Mexico relative to the US, that might well eventually reduce Mexican exports, but the main way this would happen would be firms disinvesting in production capacity there. Not expenditure switching by consumers in response to higher prices.

What Does Crowding Out Even Mean?

Paul Krugman is taking some guff for this column where he argues that the US economy is now at potential, or full employment, so any shift in the federal budget toward deficit will just crowd out private demand.

Whether higher federal spending (or lower taxes) could, in present conditions, lead to higher output is obviously a factual question, on which people may read the evidence in different ways. As it happens, I don’t agree that current output is close to the limits of current productive capacity. But that’s not what I want to write about right now. Instead I want to ask: What concretely would crowding out even mean right now?

Below, I run through six possible meanings of crowding out, and then ask if any of them gives us a reason, even in principle, to worry about over-expansionary policy today. (Another possibility, suggested by Jared Bernstein, is that while we don’t need to worry about supply constraints for the economy as a whole, tax cuts could crowd out useful spending due to some unspecified financial constraint on the federal government. I don’t address that here.) Needless to say, doubts about the economic case for crowding-out are in no way an argument for the specific deficit-boosting policies favored by the new administration.

The most straightforward crowding-out story starts from a fixed supply of private savings. These savings can either be lent to the government, or to business. The more the former takes, the less is left for the latter. But as Keynes pointed out long ago, this simple loanable-funds story assumes what it sets out to prove. The total quantity of saving is fixed only if total income is fixed. If higher government spending can in fact raise total income, it will raise total saving as well. We can only tell a story about government and business competing for a given pool of saving if we have already decided for some other reason that GDP can’t change.

The more sophisticated version, embodied in the textbook ISLM model, postulates a fixed supply of money, rather than saving. [1] In Hicks’ formulation, money is used both for transactions and as the maximally liquid store of wealth. The higher is output, the more money is needed for transactions, and the less is available to be held as wealth. By the familiar logic of supply and demand, this means that wealthholders must be paid more to part with their remaining stock of money. The price wealthholders receive to give up their money is interest; so as GDP rises, so does the interest rate.

Unlike the loanable funds story with fixed saving, this second story does give a logically coherent account of crowding out. In a world of commodity money, if such ever was, it might even be literally true. But in a world of bank-created credit money, it’s at best a metaphor. Is it a useful metaphor? That would require two things. First, that the interest rate (whichever one we are interested in) is set by the financial system. And second, that the process by which this happens causes rates to systematically rise with demand. The first premise is immediately rejected by the textbooks, which tell us that “the central bank sets the interest rate.” But we needn’t take this at face value. There are many interest rates, not just one, and the spreads between them vary quite a bit; logically it is possible that strong demand could lead to wider spreads, as banks stretch must their liquidity further to make more loans. But in reality, the opposite seems more likely. Government debt is a source of liquidity for private banks, not a use of it; lending more to the government makes it easier, not harder, for them to also lend more to private borrowers. Also, a booming economy is one in which business borrowers are more profitable; marginal borrowers look safer and are likely to get better terms. And rising inflation, obviously, reduces the real value of outstanding debt; however annoying this is to bankers, rationally it makes them more willing to lend more to their now less-indebted clients. Wicksell, the semi-acknowledged father of modern central banking theory, built his big book around the premise that in a credit-money system, inflation would give private banks no reason to raise interest rates.

And in fact this is what we see. Interest rate spreads are narrow in booms; they widen in crises and remain wide in downturns.

So crowding out mark two, the ISLM version, requires us to accept both that central banks cannot control the economically relevant interest rates, and that private banks systematically raise interest rates when times are good. Again, in a strict gold standard world there might something to this — banks have to raise rates, their gold reserves are running low — but if we ever lived in that world it was 150 or 200 years ago or more.

A more natural interpretation of the claim that the economy is at potential, is that any further increase in demand would just  lead to inflation. This is the version of crowding out in better textbooks, and also the version used by MMT folks. On a certain level, it’s obviously correct. Suppose the amount of money-spending in an economy increases. Then either the quantity of goods and services increases, or their prices do. There is no third option: The total percent increase in money spending, must equal the sum of the percent increase in “real” output and the percent increase in average prices. But how does the balance between higher output and higher prices play out in real life? One possibility is that potential output is a hard line: each dollar of spending up to there increases real output one for one, and leaves prices unchanged; each dollar of spending above there increases prices one for one and leaves output unchanged. Alternatively, we might imagine a smooth curve where as spending increases, a higher fraction of each marginal dollar translates into higher prices rather than higher output. [2] This is certainly more realistic, but it invites the question of which point exactly on this curve we call “potential”. And it awakens the great bane of postwar macro – an inflation-output tradeoff, where the respective costs and benefits must be assessed politically.

Crowding out mark three, the inflation version, is definitely right in some sense — you can’t produce more concrete use values without limit simply by increasing the quantity of money borrowed by the government (or some other entity). But we have to ask first, positively, when we will see this inflation, and second, normatively, how we value lower inflation vs higher output and income.

In the post-1980s orthodoxy, we as society are never supposed to face these questions. They are settled for us by the central bank. This is the fourth, and probably most politically salient, version of crowding out: higher government spending will cause the central bank to raise interest rates. This is the practical content of the textbook story, and in fact newer textbooks replace the LM curve — where the interest rate is in some sense endogenous — with a straight line at whatever interest rate is chosen by the central bank. In the more sophisticated textbooks, this becomes a central bank reaction function — the central bank’s actions change from being policy choices, to a fundamental law of the economic universe. The master parable for this story is the 1990s, when the Clinton administration came in with big plans for stimulus, only to be slapped down by Alan Greenspan, who warned that any increase in public spending would be offset by a contractionary shift by the federal reserve. But once Clinton made the walk to Canossa and embraced deficit reduction, Greenspan’s fed rewarded him with low rates, substituting private investment in equal measure for the foregone public spending. In the current contest, this means: Any increase in federal borrowing will be offset one for one by a fall in private investment —  because the Fed will raise rates enough to make it happen.

This story is crowding out mark four. It depends, first, on what the central bank reaction function actually is — how confident are we that monetary policy will respond in a direct, predictable way to changes in the federal budget balance or to shifts in demand? (The more attention we pay to how the monetary sausage gets made, the less confident we are likely to be.) And second, on whether the central bank really has the power to reliably offset shifts in fiscal policy. In the textbooks this is taken for granted but there are reasons for doubt. It’s also not clear why the actions of the central bank should be described as crowding out by fiscal policy. The central bank’s policy rule is not a law of nature. Unless there is some other reason to think expansionary policy can’t work, it’s not much of an argument to say the Fed won’t allow it. We end up with something like: “Why can’t we have deficit-financed nice things?” “Because the economy is at potential – any more public spending will just crowd out private spending.” “How will it be crowded out exactly?” “Interest rates will rise.” “Why will they rise?” “Because the federal reserve will tighten.” “Why will they tighten?” “Because the economy is at potential.”

Suppose we take the central bank out of the picture. Suppose we allow supply constraints to bind on their own, instead of being anticipated by the central planners at the Fed. What would happen as demand pushed up against the limits of productive capacity? One answer, again, is rising inflation. But we shouldn’t expect prices to all rise in lockstep. Supply constraints don’t mean that production growth halts at once; rather, bottlenecks develop in specific areas. So we should expect inflation to begin with rising prices for inputs in inelastic supply — land, oil, above all labor. Textbook models typically include a Phillips curve, with low unemployment leading to rising wages, which in turn are passed on to higher prices.

But why should they be passed on completely? It’s easy to imagine reasons why prices don’t respond fully or immediately to changes in wages. In which case, as I’ve discussed before, rising wages will result in an increase in the wage share. Some people will object that such effects can only be temporary. I’m not sure this makes sense — why shouldn’t labor, like anything else, be relatively more expensive in a world where it is relatively more scarce? But even if you think that over the long-term the wage share is entirely set on the supply side, the transition from one “fundamental” wage share to another still has to involve a period of wages  rising faster or slower than productivity growth — which in a Phillips curve world, means a period above or below full employment.

We don’t hear as much about the labor share as the fundamental supply constraint, compared with savings, inflation or interest rates. But it comes right out of the logic of standard models. To get to crowding out mark five, though, we have to take one more step. We have to also postulate that demand in the economy is profit-led — that a distributional shift from profits toward wages reduces desired investment by more than it increases desired consumption. Whether (or which) real economies display wage-led or profit-led demand is a subject of vigorous debate in heterodox macro. But there’s no need to adjudicate that now. Right now I’m just interested in what crowding out could possibly mean.

Demand can affect distribution only if wage increases are not fully passed on to prices. One reason this might happen is that in an open economy, businesses lack pricing power; if they try to pass on increased costs, they’ll lose market share to imports. Follow that logic to its endpoint and there are no supply constraints — any increase in spending that can’t be satisfied by domestic production is met by imports instead. For an ideal small, open economy potential output is no more relevant than the grocery store’s inventory is for an individual household when we go shopping. Instead, like the household, the small open economy faces a budget constraint or a financing constraint — how much it can buy depends on how much it can pay for.

Needless to say, we needn’t go to that extreme to imagine a binding external constraint. It’s quite reasonable to suppose that, thanks to dependence on imported inputs and/or demand for imported consumption goods, output can’t rise without higher imports. And a country may well run out of foreign exchange before it runs out of domestic savings, finance or productive capacity. This is the idea behind multiple gap models in development economics, or balance of payments constrained growth. It also seems like the direction orthodoxy is heading in the eurozone, where competitiveness is bidding to replace inflation as the overriding concern of macro policy.

Crowding out mark six says that any increase in demand from the government sector will absorb scarce foreign exchange that will no longer be available to private sector. How relevant it is depends on how inelastic import demand is, the extent to which the country as a whole faces a binding budget or credit constraint and, what concrete form that constraint faces — what actually happens if international creditors are stiffed, or worry they might be? But the general logic is that higher spending will lead to a higher trade deficit, which at some point can no longer be financed.

So now we have six forms of crowding out:

1. Government competes with business for fixed saving.

2. Government competes with business for scarce liquidity.

3. Increased spending would lead to higher inflation.

4. Increased spending would cause the central bank to raise interest rates.

5. Overfull employment would lead to overfast wage increases.

6. Increased spending would lead to a higher trade deficit.

The next question is: Is there any reason, even in principle, to worry about any of these outcomes in the US today? We can decisively set aside the first, which is logically incoherent, and confidently set aside the second, which doesn’t fit a credit-money economy in which government liabilities are the most liquid asset. But the other four certainly could, in principle, reflect real limits on expansionary policy. The question is: In the US in 2017, are higher inflation, higher interest rates, higher wages or a weaker balance of payments position problems we need to worry about? Are they even problems at all?

First, higher inflation. This is the most natural place to look for the costs of demand pushing up against capacity limits. In some situations you’d want to ask how much inflation, exactly, would come from erring on the side of overexpansion, and how costly that higher inflation would be against the benefits of lower unemployment. But we don’t have to ask that question right now, because inflation is by conventional measures, too low; so higher inflation isn’t a cost of expansionary policy, but an additional benefit. The problem is even worse for Krugman, who has been calling for years now for a higher inflation target, usually 4 percent. You can’t support higher inflation without supporting the concrete action needed to bring it about, namely, a period of aggregate spending in excess of potential. [2] Now you might say that changing the inflation target is the responsibility of the Fed, not the fiscal authorities. But even leaving aside the question of democratic accountability, it’s hard to take this response seriously when we’ve spent the last eight years watching the Fed miss its existing target; setting a new higher target isn’t going to make a difference unless something else happens to raise demand. I just don’t see how you can write “What do we want? Four percent! When do we want it? Now!” and then turn around and object to expansionary fiscal policy on the grounds that it might be inflationary.

OK, but what if the Fed does raise rates in response to any increase in the federal budget deficit, as many observers expect? Again, if you think that more expansionary policy is otherwise desirable, it would seem that your problem here is with the Fed. But set that aside, and assume our choice is between a baseline 2018-2020, and an alternative with the same GDP but with higher budget deficits and higher interest rates. (This is the worst case for crowding out.) Which do we prefer? In the old days, the low-deficit, low-interest world would have been the only respectable choice: Private investment is obviously preferable to whatever government deficits might finance. (And to be fair, in the actual 2018-2020, they will mostly be financing high-end tax cuts.) But as Brad DeLong points out, the calculation is different today. Higher interest rates are now a blessing, not a curse, because they create more running room for the Fed to respond to a downturn. [3] In the second scenario, there will be some help from conventional monetary policy in the next recession, for whatever it’s worth; in the first scenario there will be no help at all. And one thing we’ve surely learned since 2008 is the costs of cyclical downturns are much larger than previously believed. So here again, what is traditionally considered a costs of pushing past supply constraints turns out on closer examination to be a benefit.

Third, the danger of more expansionary policy is that it will lead to a rise in the wage share. You don’t hear this one as much. I’ve suggested elsewhere that something like this may often motivate actual central bank decisions to tighten. Presumably it’s not what someone like Krugman is thinking about. But regardless of what’s in people’s heads, there’s a serious problem here for the crowding-out position. Let’s say that we believe, as both common sense and the textbooks tells us, that the rate of wage growth depends on the level of unemployment. Suppose  we define full employment in the conventional way as the level of unemployment that leads to nominal wage growth just equal to productivity growth plus the central bank’s inflation target. Then by definition, any increase in the wage share requires a period of overfull employment — of unemployment below the full employment level. This holds even if you think the labor share in the long run is entirely technologically determined. A forteori it holds if you think that the wage share is in some sense political, the result of the balance of forces between labor and capital.

Again, I’m simply baffled how someone can believe at the same time that the rising share of capital in national income is a problem, and that there is no space for expansionary policy once full employment is reached. [4] Especially since the unemployment target is missed so often from the other side. If you have periods of excessively high unemployment but no periods of excessively low unemployment, you get a kind of ratchet effect where the labor share can only go down, never up. I think this sort of cognitive dissonance happens because economics training puts aggregate demand in one box and income distribution in another. But this sort of hermetic separation isn’t really sustainable. The wage share can only be higher in the long run if there is some short-run period in which it rises.

Finally, the external constraint. It is probably true that more expansionary fiscal policy will lead to bigger trade deficits. But this only counts as crowding out if those deficits are in some sense unsustainable. Is this the case for the US? There are a lot of complexities here but the key point is that almost all our foreign liabilities (and all of the government’s) are denominated in dollars, and almost all our imports are invoiced in dollars. Personally, I think the world is still more likely to encounter a scarcity of dollar liquidity than a surfeit, so the problem of an external constraint doesn’t even arise. But let’s say I’m wrong and we get the worst-case scenario where the world is no longer willing to hold more dollar liabilities. What happens? Well, the value of the dollar falls. At a stroke, US foreign liabilities decline relative to foreign assets (which are almost all denominated in their home currencies), improving the US net international investment position; and US exports get cheaper for the rest of the world, improving US competitiveness. The problem solves itself.

Imagine a corporation with no liabilities except its stock, and that also paid all its employers and supplies in its own stock and sold its goods for its own stock. How could this business go bankrupt? Any bad news would instantly mean its debts were reduced and its goods became cheaper relative to its competitors’. The US is in a similar position internationally. And if you think that over the medium term the US should be improving its trade balance then, again, this cost of over-expansionary policy looks like a benefit — by driving down the value of the dollar, “irresponsible” policy will set the stage for a more sustainable recovery. The funny thing is that in other contexts Krugman understands this perfectly.

So as far as I can tell, even if we accept that the US economy has reached potential output/full employment, none of the costs for crossing this line are really costs today. Perhaps I’m wrong, perhaps I’m missing something. but it really is incumbent on anyone who argues there’s no space for further expansionary policy to explain what concretely would be the results of overshooting.

In short: When we ask how close the economy is to potential output, full employment or supply constraints, this is not just a factual question. We have to think carefully about what these terms mean, and whether they have the significance we’re used to in today’s conditions. This post has been more about Krugman than I intended, or than he deserves. A very large swathe of established opinion shares the view that the economy is close to potential in some sense, and that this is a serious objection to any policy that raises demand. What I’d like to ask anyone who thinks this is: Do you think higher inflation, a higher “natural” interest rate, a higher wage share or a weaker dollar would be bad things right now? And if not, what exactly is the supply constraint you are worried about?


[1] The LM in ISLM stands for liquidity-money. It’s supposed to be the combination of interest rates and output levels at which the demand for liquidity is satisfied by a given stock of money.

[2] OK, some people might say the Fed could bring about higher inflation just by announcing a different target. But they’re not who I’m arguing with here.

[3] Krugman himself says he’d “be a lot more comfortable … if interest rates were well clear of the ZLB.” How is that supposed to happen unless something else pushes demand above the full employment level at current rates?

[4] It would of course be defensible to say that the downward redistribution from lower unemployment would be outweighed by the upward redistribution from the package of tax cuts and featherbedding that delivered it. But that’s different from saying that a more expansionary stance is wrong in principle.

Rogoff on the Zero Lower Bound

I was at the ASSAs in Chicago this past weekend. [1] One of the most interesting panels I went to was this one, on Advances in Open Economy Macroeconomics. Among other big names, Ken Rogoff was there, as the discussant for a rather strange paper by Pierre-Olivier Gourinchas and Helene Rey.

The Gourinchas and Rey paper, like much of mainstream macro these days, made a big deal of how different everything is at the zero lower bound. Rogoff wasn’t having it. Here’s a rough transcript of what he said:

The obsession with the zero lower bound is encouraging all kinds of wacko ideas. People are saying that at the ZLB, productivity increases are bad (Eggertsson/Krugman/Summers), protectionism is good (Eichngreen), price flexibility is bad, and so on.

But there is an emerging literature that says economists are taking the zero lower bound too literally. In fact, getting negative rates is not that hard. So before you take seriously these, let’s say, very creative ideas, it would be simpler to think about getting rid of the zero bound.

There are lots of ways to do it. I talk about some in my book, but people already understood this back in the 1930s. There was Robert Eisler’s proposal to have banks accept cash deposits at a discount, for instance, which would have effectively created negative rates. If Keynes had read Eisler, he might have gone in a different direction. [2] It’s a very old idea — Kublai Khan did something similar. There will be pushback from the financial sector, of course, who think negative rates will be costly for them, but fundamentally it is not hard to do.

These rather striking comments crystallized something in my mind. What is the big deal about the ZLB? For mainstream macroeconomists, including Gourinchas and Rey in this paper, the reason the ZLB matters is that it prevents the central bank form setting an interest rate low enough to keep output at potential. [3] It’s precisely this that makes inapplicable the conventional analysis of a nonmonetary problem of allocating scarce resources between alternative ends, and requires thinking about other entry points. If the central bank can’t solve the problem of aggregate demand then you have to take it seriously, with all the wacko and/or creative stuff that follows.

In the dominant paradigm, this is a specific technical problem of getting interest rates below zero. Solve that, and we are back in the comfortable Walrasian world. But for those of us on the heterodox side, it is never the case that the central bank can reliably keep output at potential — maybe because market interest rates don’t respond to the policy rate, or because output doesn’t respond to interest rates, or because the central bank is pursuing other objectives, or because there is no well-defined level of “potential” to begin with. (Or, in reality, all four.) So what people like Gourinchas and Rey, or Paul Krugman, present as a special, temporary state of the economy, we see as the general case.

One way of looking at this is that the ZLB is a device to allow economists like Krugman and Gourinchas and Rey — who whatever their scholarly training, are aware of the concrete reality around them — to make Keynesian arguments without forfeiting their academic respectability. You can understand why someone like Rogoff sees that as cheating. We’ve spent decades teaching that the fundamental constraint on the economy is the real endowment of resources and technology; that saving boosts growth; that trade is always win-win; that money and finance matter only in the short run (and the short run is tolerably short). The practical problem of negative policy rates doesn’t let you forget all of that.

Which, if you turn it around, perhaps reflects well on the ZLB crowd. Maybe they want to forget all that? Maybe, you could say, they take the zero lower bound seriously because they don’t take it literally. That is, they treat it as a hard constraint precisely because they are aware that it is only a stand-in for a deeper reality.


[1] The big annual economics conference. It stands for Allied Social Sciences Association — the disciplinary imperialism is right there in the name.

[2] This was an odd thing for Rogoff to say, since of course while Keynes didn’t discuss Eisler as far as I know, he talks at length about the similar proposals for depreciating cash of Silvio Gesell and Major Douglas. Notoriously he says these “brave cranks and heretics” have more to offer than Marx.

[3] Gourinchas and Rey are reality-based enough to say “the policy rate,” not “the interest rate.”


EDIT: Added the seriously-but-not-literally phrasing as suggested by Steve Roth on Twitter.