Let me follow up on what Jim Devine and Blair Sandler have said. There are already a lot of fairly establishment economists, including an increasing number who are somewhere right of center, who accept that "NAIRU can change," which kind of vitiates the concept as a policy holy grail. The current line is probably, "Yes there is a NAIRU, but it shifts with conditions," and in an older argument less accepted, in response to the state of past unemployment. This is the hysteresis or persistence argument (now, bill, let's not have a technical lecture here on trend stationarity vs difference stationarity!). The NRU is supposedly the rate to which the economy will "naturally" go if it is an unregulated laissez-faire state. According to the Friedman and his ilk that should reflect some normal level of frictional and structural unemployment. But, although there has been a strong tendency to identify the two, there is nothing in theory to show that they would necessarily be one and the same, even if we grant their existence. They do not have to equal each other and they can both change. So, why bother with them? Obviously, they do become a cover for justifying the reserve army in the hands of most economists, but their essential emptiness is becoming increasingly apparent. Barkley Rosser -- Rosser Jr, John Barkley [EMAIL PROTECTED]