Denne grafen er laget av Nate Silver ved ‘FiveThirtyEight’ bloggen, en politisk/statistisk blogg nylig kjøpt av NY Times. Grafen viser de siste 10 årene med sysselsettingsrapporter fra Bureau of Labour Statistics i USA. Deretter gjør han et Google News søk og finner hva økonomer forventet før hver rapport og finner deretter ut om de var for optimistiske eller pessimistiske.
With the larger sample size, we can now say almost without question that the jobs creation estimates put forward by economists have been biased upward. Negative surprises have been about twice as common as positive ones over the past 12 years.
What’s interesting is that this pattern is fairly persistent across time: the study covers portions of three expansions and two recessions, and the optimism bias is present in all five periods. If anything, it’s gotten a little bit milder recently: economists were especially flummoxed when the jobs engine of the 1990s began to screech to a halt at the start of the 2000s.
The error in economists’ forecasts of the payrolls number, and the error in the figure as originally reported by the government versus the revised number, tend to have a compounding effect. Since 2000, economists’ initial estimate of job growth has been off by an average of 90,000 jobs as compared with the revised figure. That implies that when you see an economist’s forecast of monthly job growth, it has a 95 percent confidence interval of plus or minus 232,000 jobs.
Når økonomien svinger mer enn vanlig, er også ‘feilene’ større.
Kan du tenke andre områder av økonomien vi kan utvide denne tankegangen til?