Brad de Long reports on a dinner discussion with Paul Krugman and Janet Yellen, hinking About Puzzling Anomalies in the Flow of Macroeconomic Data . He says
We currently have two large, puzzling anomalies in the macroeconomic dataflow. First, productivity growth is ludicrously, ridiculously, unbelievably rapid. Second, the high current level of the U.S. trade deficit fits very uneasily with the relatively high value of the dollar and the lack of large interest rate differentials in favor of the U.S. relative to other countries
and says
Things that readers think are smart should be attributed to Paul Krugman or to Janet Yellen. Things that people think are dumb should be attributed to me.
. At the risk of showing myself up as dumb (at least relative to these very smart guys), I don’t see a problem in either case.
Beginning with productivity, it’s only labour productivity that’s grown rapidly and seemingly anomalously. Capital productivity has declined markedly, as has multifactor productivity (a weighted average of capital and labour productivity) In part this reflects the economics of embodied technical change – as computing power has become cheaper it has been applied more intensively. But there’s also a big hangover effect from the bubble and bust, when crazy signals from capital markets led lots of firms to undertake unprofitable investments. Once some semblance of reality returns, the natural response is to cut back and it’s much easier to sack the least productive workers than to reduce capital stock. So labour productivity rises fast, but output growth is weak. I’ve done the numbers here (see also here and here), and they fit the data neatly.
On the absence of a large interest rate differential and the relatively high value of the dollar despite the large deficit, this is only a problem if you assume capital markets operate rationally. All the recent evidence is against this assumption, but in any case the markets aren’t as crazy as all that. Most non-US participants are now selling US-denominated assets ,which are only being kept afloat by the efforts of Asian central banks. Strong versions of the efficient markets hypothesis would suggest that such activities must be futile, and that speculators, anticipating the inevitable decline of the dollar would drive the central banks to the wall, but I don’t have any problem ignoring strong versions of the efficient markets hypothesis.