というGreg IpのWSJ記事(原題は「Sometimes, Boosting Supply Requires More Demand」)をEconomist's Viewが紹介している

The Federal Reserve, everyone agrees, can boost growth in the short run. But can it do it over the long run? This once heretical concept is the latest argument in favor of the Fed taking its time about raising interest rates.

Traditionally, economists treated supply and demand as separate matters. ... The Fed, in this traditional view, can affect how demand fluctuates around the long-run trend, but it can’t affect the long-run trend itself.

But in real life, supply and demand are not so easily separated. The labor force is a function not just of the number of people of working age (a supply-side factor), but also how long they’ve been unemployed and thus how useful their skills are (a demand-side factor). Business investment in new equipment isn’t just a function of the state of technology (a supply side factor), but what they anticipate sales to be in coming years (a demand side factor).

This means that policies that affect demand in the short run can, conceivably, affect supply in the long run, as well. ...
Jay Powell, a Fed governor, makes the point in a speech last week. ... Mr. Powell suggests, the Fed should not assume capacity is written in stone and immune to monetary policy: “Should we think of this supply-side damage as permanent or temporary?” he said in his speech last week. “It seems plausible that at least part of the damage can be reversed. ...

This means, Mr. Powell says, the Fed should be more skeptical than usual when superficial evidence suggests the economy is approaching capacity. While he dances around the implications for monetary policy a bit, the conclusion is obvious: the Fed should stay easier, for longer, which should “not only help restore some of our economy’s potential,” but get inflation back up to 2% faster.

Mr. Powell’s logic is quite compelling and provides an important reason why the Fed should err on the side of letting unemployment fall well below traditional measures of the “natural rate” of unemployment before tightening. ...

FRBが短期的に成長を押し上げることができるという点については衆目の一致するところである。しかし長期的にもそれが可能だろうか? これはかつては異端の考え方であったが、今ではFRBが利上げに時間を掛けることを支持する最新の主張となっている。

Economist's ViewのMark Thomaは、自分が以前のエントリでこの点を主張したことを指摘したほか(cf. ここ)、そのエントリに言及したデビッド・ベックワースの昔のエントリにもリンクしている。


  • 金融危機の後だけでなくすべての景気後退の後で推計された潜在力は低下する。これは景気後退が潜在力を押し下げただけでなく、景気後退の前に潜在力が過大に推計されていた影響もあるはず。
  • 大抵の景気後退では金利はゼロまで下がらない。もし需要不足が潜在力を押さえつけていたならば、FRBはもっと金利を切り下げたはず。需要が供給に影響するだけでなく、供給も需要に影響する。