The Financial Times reports this morning that the Olympics don't seem to be leading to quite the tourist boom expected :
The games have attracted as many as 100,000 foreign visitors [per day] to London – more than in previous Olympics. But, on its own, that number significantly lags behind the estimated 300,000 foreign tourists [per day] who could be expected in a typical year.
As Richard Murphy points out , this means that one of the great hopes for bringing the country out of recession appears to be fading away. Which means the word of the day is hysteresis.
In general terms, hysteresis is similar to intertia; it is the concept that some things which are hard to get going may then require little input to maintain, and even more effort to reverse.
In specific economic terms, it is the theory that persistent levels of high unemployment raise the "natural" rate of unemployment, also known as NAIRU, the non-accelerating inflation rate of unemploymet. This is the level of unemployment at which, under neo-classical economics, inflation stays low and steady. (As a side-note, yes, neo-classical economics holds that a certain amount of unemployment is good. "Full employment" is thus a bad thing, because it leads to spiralling inflation)
Although it's not specifically related to GDP, it is always a fear when dealing with persistent unemployment and long periods of stagnation and recession. The cause of the phenomenon comes when layoffs in a particular sector increase the bargaining power of the remaining workers. as there are fewer of them left, they can demand higher wages, which become "sticky" in nominal terms, if the period of unemployment lasts long enough. If, at the end of the recession, the business then wants to hire new employees, they have to pay them the new, high wage. In practice, this means that either unemployment stays high permanently, or inflation goes up until the value of the high wage is back, in real tems, to where it was.
It doesn't look like we are seeing the "increased wages" part of the problem yet (since wages are very much stagnating), but that hasn't stopped Citigroup's Ajai Chopra warning everyone :
Our analysis of such hysteresis effects shows that the large and sustained output gap, the difference between what an economy could produce and what it is producing, raises the danger that a downturn reduces the economy’s productive capacity and permanently depresses potential GDP.