The government in Germany some years ago messed around with the data and the data set until all appeared well and some parts of the unemployed population - apparantly mostly the long-time unemployed, who have no motivation left to ever leave the welfare benefits system to work again - were just dropped from the data set. Recognize that unemployment data is a government tool. It's one of many interesting data points for one's analysis of the economic situation, but by itself it's pretty meaningless as it's not consistently measured over time.
Here's an excellent article detailing how the government over the past 40 years or so has been changing the measurements of our basic economic indicators: http://harpers.org/archive/2008/05/0082023