サンフランシスコ連銀総裁のジョン・ウィリアムズが自然利子率の低下に関する表題の小論を書き、話題を呼んでいる(原題は「Monetary Policy in a Low R-star World」;cf. ロイター日本語紹介記事FT社説邦訳)。

これにサマーズが反応し、「考えさせられる小論(A Thought Provoking Essay)」だ、としながらも、その提案を以下のように批判的に取り上げている。

Wlliams rightly if rather tentatively draws the conclusions that a chronically very low neutral rate has important policy implications. He stresses the desirability of raising r* by pursuing structural policies to raise growth and affirms the importance of fiscal policy. I yield to no one in my enthusiasm for improved education and educational opportunity but I do not think it is plausible that it will change the neutral rate appreciably in the next decade given that the vast majority of the 2030 labor force will be unaffected.
If Williams is overenthusiastic on education, he is under enthusiastic on fiscal stimulus. He fails to emphasize the supply side benefits of infrastructure investment that likely enable debt financed infrastructure investments to pay for themselves as suggested by DeLong and Summers and the IMF. Nor does he note at current interest rates an increase in pay as you go social security could provide households with higher safe returns than private investments. More generous Social Security would likely reduce the saving rate, thereby raising the neutral interest rate with no change in budget deficits. Nor does Williams address the possibility of tax measures such as incremental investment credits or expansions in the EITC financed by tax increases on those with a high propensity to save. The case for fiscal policy changes in the current low r*’environment seems to me overwhelming and much can be accomplished without any increase in deficits.


Yet as Larry says, the paper is still weak and tentative even on monetary policy, to an extent that’s hard to understand:

[The benefits of a higher target have increased and so far as I can see nothing has happened to change the cost of a higher target,]
I am disappointed therefore that Williams is so tentative in his recommendations on monetary policy. I do understand the pressures on those in office to adhere to norms of prudence in what they say. But it has been years since the Fed and the markets have been aligned on the future path of rates or since the Fed’s forecasts of future rates have been even close to right. [I cannot see how policy could go badly wrong by setting a level target of 4 to 5 percent growth in nominal GDP and think that there could be substantial benefits. (I expect to return to this topic in the not too distant future)]

Furthermore, there’s basically no break with orthodoxy on fiscal policy, despite the evident importance of the liquidity trap, evidence that multipliers are fairly large, and basically zero real borrowing costs.
Yet Williams is at the cutting edge of policy rethinking at the Fed. And in general mainstream thinking about macroeconomic policy has changed remarkably little, remarkably slowly.
You might say that it is always thus. But, you know, it isn’t.






*2:クルーグマンが引用したのは「I am disappointed therefore...even close to right.(そのため〜昔の話である。)」の部分だけだが、それだけではサマーズの真意がやや伝わりにくいと思われたため、ここでは[]で括った前後の引用を足してある。