しょっちゅう意見を変えるクルーグマンだが、今度は自分の1998年の論文を全面的に否定している：
But those of us who started worrying about liquidity traps in the face of Japan’s experience were well aware of that pitfall. In fact, I wrote down my original liquidity trap model starting from a firm belief that the liquidity trap was nonsense: even if the interest rate is zero, I thought, increasing the money supply must raise demand. So I set out to write a model with all the i’s dotted and t’s crossed, so as to demonstrate that point ― and found, to my shock, that the model actually said the reverse.

What comes down to is this: once you’ve pushed the short-term interest rate down to zero, money becomes a perfect substitute for short-term debt. And any further increase in the money supply therefore displaces an equal amount of debt, with no effect on anything. Period, end of story.
ゼロ金利では、貨幣と国債は完全代替的になるので、いくら日銀が通貨を供給しても何も起こらない。したがって（インフレを起こせない）日銀がインフレ目標を宣言しても、credible commitmentにはならないのだ。これは10年前から、植田和男氏などが指摘していたことだ。今回のデフレでは、岩田規久男氏も原田泰氏もインフレ目標をいわなくなった。不毛で愚劣な「インタゲ論争」も、これでやっと終わりかな。