Although not being a homogenous theory, most papers and scholars related to MMT share some views and concepts. I willl briefly describe some components and critically comment them. This is insofar a risky endeavor as I am not coming from “inside” MMT but being a curious and open-minded economist, open also for heterodox ideas, though having difficulties in understanding what the “T” in MMT really is. Moreover, MMT stems from Post-Keynesian (PK) economics and thus sharing the legacy of a tradition to create its own, partially incommensurable terminology and to reject critique by asserting that it is based on a misunderstanding. Anyway, I have nothing to lose, so here is my critical summary from a personal point of view. Each point starts with an important MMT element (in Italics) which is then discussed.

1) Banks are not channeling funds from savers to investors, hence the “Loanable Funds Theory” (LFT) is flawed. Instead, deposits (money) are created by banks by providing credits or buying bonds from non-banks. This induces a demand for reserves which can be created by the central bank only. The central bank (CB) will fully accommodate the demand for reserves as their primary operating tool is the interest rate. If CB would try to “control” the monetary base it would lose control over the short-run interest rate. Thus, money is something endogenous while the short-run rate is controlled by the CB. The famnous “money multiplier” is just an algebraic relationship but the story one can find in old and outdated textbooks that the CB does not only determine M0 but also M via the multiplier, is flawed. The causality runs the other way round.

I fully agree! However, this view is mainstream and not specific to MMT. This is part of my courses since years even before I ever heard about “MMT”. One can find it in standard textbooks as well as in publications e.g. of the Deutsche Bundesbank or the Bank of England. It is also the main reason why in modern New Keynesian macroeconomics the old LM curve is replaced by an interest rate rule of the CB. It has always been a puzzle for me why the simple description of daily acounting practices of banks is a scientific “discovery” and a “theory” how money is created. Anyway, it is good that somebody enunciates that.

But there are some caveats:

• One should keep in mind that “full accomodation” of reserve demand is a behavioral trait of most central banks around the world which are committed to Inflation Targeting. If, for example, a CB would adopt a position where interest rates are just a market price while the operative goal is to control M, things would be different. So the MMT view is a correct description of the current fractional reserve banking system and the current paradigm of practical CB policies. But it would become inappropriate if this paradigm would change. Example: before the Global Financial Crisis, the ECB and fomerly the Deutsche Bundesbank did not guarantee a “full allotment” when commercial banks applied for central bank credits.

• In MMT, the Post-Keynesian “horizontalist position” is adopted: commercial bank’s credit supply is fully elastic, thus the money volume is only determined by money demand. But there is no need for this oversimplisric view. Considering technical details of loan creation such like calculating risk premia, collateralization, credit risk standards, maturity mismatch effects, capital constraints, portfolio balancing effects etc., also upwards sloped credit supply curves and rationing effects could be considered. Thus, the long-run interest rate for risky assets which is highly important for decisions in the real sector, is just “influenced” by the CB but not determined. Mainstream financial economics have much more elaborated models of banking’s credit supply behavior than the “horizontalist approach”.

• With the enormously grown shadow-banking sector, commercial banks have alternatives to borrow liquidity which influences their demand for reserves. Moreover, the interest-rate strategy of CBs is typically anchored at a “natural rate”. These arguments give reason to believe that even the short-run rate is not purely exogenously determined by the central bank, but in a certain sense the CB is also following a long-run market developments.

• There is meanwhile a huge amount of credits provided by “shadow banks”, i.e. finance companies. Here, the LFT fully applies: these financial institutions issue papers in order to raise funds which are then lend out. One should keep in mind that this sector provides a quite close substitute to “normal” credits by depository banks. And this has an impact on the long-term rate which is also targeted by the CB. A realistic model of the financial market (and thus monetary policy transmission) has to take this into consideration.

• The rejection of LFT is often expressed by the claim that “banks are not intermediates”. This is true only in the sense that they do not channel resources from A to B. But they could be considered as intermediates as they are doing asset transformation (lot size, maturity, risk, liquidity transformation) and partially solving or mitigating principal-agent problems. In this sense I (and many textbooks) still use the term “intermediate”.

2) Fiscal expenditures are operated by the central bank by creating money while tax revenues are reducing money. Thus, one should think about the fiscal and monetary operations as one unit. Fiscal expenditures have therefore not to be “financed” by (current or future) taxes, and the fiscal budget is not “constrained”. The budget is G + iD = T + ΔD + ΔM, and it is a decision of the “sovereign state” to decide about these components. [G = gov. expenditures, D = public debt (bonds), T = tax revenues, M = money (own currency), i = interest rate on public debt]

Yes, MMT is right when saying that in daily practice (!) fiscal expenditures are operated by the central bank just by creating and transferring money. There is a permanent flow of governmental expenditures and also a permanent inflow of taxes and inflow of money as a result of issuing bonds. As this is not perfectly synchronized, we see on the central bank’s balance sheet a permanent creation and destruction of money. That is a description of accounting practice, not a “theory”. I cannot see this as a “scientific point of view”. And nothing specific follows from this practice. Imagine, that the same operations are done by a commerical bank which is willing to handle the government’s budget. The ΔM in the equation is then the government’s bank credit which has created additional deposits. But in this case it would become evident that there is a (limited) credit line, and a credit has to be served and paid back. Insofar there is a constraint by tax revenues, the ability to place new bonds (which also have to be served and paid back), and the bank’s credit line. The MMT’s semantic that – in contrast to a private household which doesn’t have an account at the central bank – governmental expenditures do not have to be “financed” and that there are no constraints, is more confusing than clarifying the operations. It is better to say that expenditures have not to be “pre-financed” by taxes. And it is legitimate to say that the fiscal authority is “not constrained” in the expenditures if and only if the legislation allows for unlimited monetization of public debt. But the latter is not the case in most countries, and the (non) allowance doesn’t follow from the accounting practice. Likewise the claims about the endogeneity of money and the accomodative behavior of CBs are grounded in the observed (legal) practice, MMT should also respect the legal practice of non-allowance of monetization of public debt in most countries.

The thing is now that MMT rejects this practice and declare the opposite as the “natural state” and also as a normative benchmark:

3) A sovereign state which is able to issue its own currency can never get insolvent. This is because one have to think fiscal and monetary operations as one unit (see above). Henceforth, the government could do everything necessary to manage aggregate demand wthout being constrained by the budget, without being dependent on the private capital market, and thus without any risk to get insolvent.

Yes, MMT is completely right – but only in a ficticious world where unlimited monetization of public debt is allowed which implies that central banks are not independent. Consequently, MMT offers explanations of macroeconomic problems arising from institutional arrangements where the state isn’t “sovereign”, i.e. if central banks are independent, or even worse, if national fiscal policies cannot be coordinated with a supranational monetary policy like in the case of the Eurozone which is seen as dysfunctional construction.

In which sense this is “theory”? Or is it more a political suggestion, an agenda how to design monetary and fiscal institutions and rules? The clause “If sovereign … then not constrained” sounds like a theory but it isn’t much more than a tautology as MMT proposes a new semantic what “sovereign” means. As the term implies total “fiscal dominance” (in mainstream terms) or unlimited automatic bailout, the theoretical claim that a sovereign state cannot get insolvent (if indebted in domestic currency) is a tautology or at least trivial. In this sense, neither the Eurozone countries, nor e.g. Germany at times of the Deutsche Mark are considered as sovereign countries – thus, the MMT view is confirmed. The narrative is always confirmed. That’s the problem rather than the advantage.

What is really annoying is that MMT largely ignores the literature of the last decades about time-inconsistency and principal-agent problems, the role of credibility in monetary policy transmission, the political economy of (fiscal) policy making in democracies, also some empirical issues such like the fact that nearly all episodes of hyper-inflation occurred in systems with unlimited monetization of public debt. Thus, they are largely ignoring economic arguments in favor e.g. of CB independence. It appears as if the “mainstream” wasted an enormous amount of time and human capital in the last decades in order to analyse problems which would not exist if neoliberal mainastream economists would not have pushed policy to make states being non-sovereign.

Instead, the MMT view is surprisingly super-simple: the government is benevolent, omnipotent, and has just to manage aggregate demand in order to heal nearly every macroeconomic problem because nearly all problems stem from the demand side. And the necessary fiscal opetrations are unconstrained thanks to the CB which is accomodating any fiscal budget, if necessary by creating money. From this point of view, all deviating positions which are summarized as “mainstream” are thus blamed as being “neoliberal ideologies” or based on naive perceptions of a “Swabian housewife” (making it difficult to really communicate with economists outside the own bubble).

The wording, the own semantic, the ignorance of large parts of the literature contributes a lot to the picture that MMT is more a cult rather than a serious theory. That’s a pity because some elements could contribute to scientific progress. The ideological pride to be “non-mainstream”, and adopting the Post-Keynesian academic legacy which is best characterized by Monty Python’s “Life of Brian” where the biggest enemy of the Judean People’s Front is the People’s Front of Judea, also hinders MMT to be recognized as a potentially valuable academic contribution.

4) Debt of one entity are claims (or wealth) of the other. Hence, public debt is (part of) private wealth.Also expenditures of one entity are income of the other.

I cannot believe that this triviality is regarded to be an “insight” of a “scientific theory”. This is part of an economics 101 course when describing the national accounting system.

5) An open economy like Germany cannot permanently run a trade surplus and having a balanced fiscal budget. They are forcing other countries to get more and more indebted. So if the private sector has a “surplus”, and trade should be balanced in the long run, the governemnt must run a deficit. Therefore debt brakes and the ideology of “balanced budgets” (like the “Swabian housewife”) are undermining macroeconomic stability. The “German strategy” to run balanced fiscal budgets and to achieve a trade surplus at the same time is a “neo-merkantilist” strategy which cannot be recommended. It requires that there are deficit countries, willing to get more and more indebted.

Usually, this argument is explained by excessively re-iterating the national book-keeping equation S = I + Ex – Im in various forms, and disentangling private and public savings: S = S_p + (T – G). However, an algebraic relationship from national accounting system isn’t yet a theory. All conclusions one can directly draw from it, are trivial. Of course a large and permanent trade surplus might be problematic in terms of macroeconomic equilibrium. Many economists and international institutions are concerned about the German surplus, even without any reference to MMT. However, the intertemporal approach to the balance of payments shows that trade imbalances (for a certain time) could be efficient for both trade partners. Unfortunately, the terms “surplus” and “deficit” have a strong normative connotation.

The claim of a “German strategy” which is “neo-merkantilist” suggests that the country is acting just like one economic unit, instead of considering millions of single (domestic and foreign) economic decisions. Or it suggests that the government is able to strategically determine the overall empirical picture. For example, the success of the German export sector is explained by too low wages. Although there might be some truth in this argument, it neglects that also other factors such like high productivity and/or high quality might also play a role. Wages are contracted, not set by the government. However, there might be indirect effects such like dampening the wage dynamics through Agenda 2010 labor market reforms. But the goal of these reforms have been the reduction of unemployment rather than “neo-merkantilist” goals. The former is achieved while the trade surplus might be seen as an unwarranted side effect.

So if in the long run (Ex – Im) should be close to zero, and the private sector runs a “surplus” S_p – I > 0, then it is seen as necessary that the government runs a deficit T – G < 0. However, this is algebra, not theory, and no policy agenda follows from that. A supply side economist would argue that policy should stimulate private investments and thus bringing S_p – I close to zero. There are several policy options being consistent with the algebra of the accounting system. By the way: in some texts there is confusion about the term “surplus” which is sometimes identified with savings which requires “debt” of another entity. That’s wrong. Example: zero public and private household savings, zero net exports, but firms have positive savings which are equivalent to their own net investment. No debt is involved.

6) MMT rejects the idea of crowding out. Crowding out only happens if the economy is at it’s capacity limits.

It is argued that there cannot be an interest-rate based crowding out effect as the interest rate is controlled by the CB. A crowding out by deficit spending because placing new sovereign bonds in the market will reduce private financing – both are competing for saver’s funds – is also rejected. Public spending financed by the money press will not reduce the demand for corporate bonds. Moreover, private activities could be easily financed by fully elastic credit supply. True, but if public debt is not monetized, and if credit supply isn’t fully elastic, the argument does not hold. In addition, many MMT proponents argue that aggregate demand does not depend on the real interest rate (vertical IS curve). Henceforth, even increasing long-term rates will not have a dampening effect. The reason why aggregate demand is not tied to the interest rate (no intertemporal deliberations of consumers/savers and investors at all? Really?) remain unclear. So the problem of potential crowding out is more or less assumed away by declaring all possible economic transmission channels as being irrelevant or inexistent. The atitude is not to say: yes, there are multiple potential economic mechanisms, but I consider them as empirically less relevant. Instead, the attitude is more apodictic: it’s not just empirical evidence, it’s a deep theoretical insight. The numerous econometric estimates of fiscal multipliers which should be quite large in absence of any crowding out effects, but in fact turned out to be relatively small, seem not to be well recognized.

By the way, if aggregate demand does not depend on the interest rate, there is not much room for interest-rate based monetary policy to stimulate aggregate demand like in mainstream models. The main transmission channel is simply regarded as being inexistent. Monetary policy becomes ineffective and has to be replaced by fiscal policy. It just serves as an “assistant” for the fiscal authority. But then the question arises, if this is really true, why do central banks then accomodate each reserve demand in order to keep control over the interest rate? If this ttransmission channel is inexistent? I can imagine the answer: because they are believing in the wrong mainstream model. But then central banks believing in and acting according to a “wrong” model are a cornerstone of the “correct” MMT model?

7) MMT largely rejects the Phillips Curve.

So all attempts for detalied (micro-) economic explanations of this curve are simply wiped away as being irrelevant. Also empirical evidence about ties between output and inflation is irgnored. It is a general and very remarkable attitude of MMT and also (largely) PK economics that there is a lack of deliberated and diligent econometric analysis. While in the last decades “evidence based” macroeconomics got growing importance (and thus being much more flexible with respect to “ideological” positions), MMT/PK publications often look at aggregated macroeconomic time series by eye-balling, seeking for evidence confrming their narratives. I wouldn’t regard that as empirical research on a competitive level. Perhaps I am wrong, I am not an expert in this field, but I still haven’t found somebody to convince me about the opposite.

Once when the Phillips Curve is rejected, life becomes very easy: as there is no goal conflict between unemployment and inflation any longer, also the time-inconsistency and agency problems which lead to the central bank independence literature can be happily ignored. Without goal conflicts, we also do not need a solution of the assignment problem, so why not bundling fiscal and monetary policy to one unit? This isn’t a highly problematic vision any longer once when we have assumed away all severe problems this might induce.

If there is no Phillips Curve trade-off, and the fiscal budget is not constrained, any measures of deficit-spending at any size could be recommended in order to bring down unemployment. Very easy! And if inflation starts to rise, MMT suggests to rise taxes which then reduces the money stock (see point 2). Henceforth, fiscal policy is assigned to both targets, employment and price stability, while monetary policy just accomodates it. The interesting point is that this establishes a strong tie between money and inflation likewise in the quantity equation approach. But in contrast to the monetarist approach, MMT suggests that money creation (for fiscal reasons) do have a real effect on the output. I would see here a slight contradition to the money endogeneity approach where the causality runs from output and price level to money demand and thus money supply, rather than from money supply to output and price level.

8) Parts of MMT suggests a public job guarantee. The government could hire any amount of workers until the capacity limits are reached. Payment of these workers (usually minimum wages) isn’t a problem because the governmental budget is not constrained. In case of need, it is financed by the central bank.

This is clearly not “theory” but a (left) political agenda. All problems associated with such a program (e.g. crowding out private competitors) should not be discussed here. My aim is just to discuss the status as a valuable theory.

Summing up, there are some valuable insights, i.e. point 1), but they are mainstream and widely accepted. There are also interesting insights into practical ties between fiscal and monetary operations, see point 2), which deserve more attention, although I don’t believe that fundamental theoretical insights can be derived from that. Even the highly critical point 3) could be fruitful if communicated in a much less doctrinaire manner. Nobody will be willing to recognize arguments speaking in favor of e.g. an arrangement where the CB is allowed to buy public debt on the primary market without any danger of moral hazard or fiscal dominance (e.g. as a standard procedure to create reserves such that the interest rate goal is achieved), or allowing CB to be the lender of last resort, if one either has to decide to remain a “mainstream enemy” or to convert to the gospel truth of an MMT cult. There are too many aspects of the new “paradigm” which makes it scientifically non-competitive. Therefore, MMT should not set hope on a “paradigm shift”. I am more in favor of Imre Lakatos’ concept of a research program where the core of the program could change due to a rational discussion of arguments. But then a lot has to be changed in communication and wording. In my personal view, the mainstream can learn much more from PK’s ideas of effective demand, fundamental uncertainty, and heuristic behavior rather than from MMT.