WASHINGTON (AP) — Despite weak job growth in the three years since the recession officially ended, unemployment rates for most groups of Americans — white, black and Hispanic, young and old — have fallen. But their rates haven't fallen equally or for the same reasons.

Asian-Americans have enjoyed the sharpest drop in unemployment, followed by Hispanics and whites.

The unemployment rates for Asians and Hispanics fell because more people in each group found jobs. But the rate for whites fell for a different reason: More of them stopped looking for jobs or left the work force for other reasons, such as retirement. People who are out of work aren't counted as unemployed if they've stopped looking for a job.

The unemployment rate for African-Americans fell the least. More blacks got jobs. But unlike other groups, the number of unemployed African-Americans also rose. That suggests that unemployed blacks weren't as likely as others to give up their job searches and leave the work force. The proportion of African-Americans in the work force fell the least for any group.

Among age groups, Americans ages 55 and older have fared best since the recession ended. Their unemployment rate hasn't fallen as much as for those ages 25-54. But it's dropped for a more encouraging reason: More of them are employed. By contrast, the unemployment rate for those ages 25 through 54 has fallen mostly because more of them stopped looking for a job.

Among industries, the one that's produced the most jobs in the past three years has been temporary help services. Temp jobs have jumped 45 percent. No other industry is even close. Economists generally view more temp hiring as an encouraging sign, because companies usually add temps before they hire permanent workers.

The next-biggest source of job gains is educational services. This category consists of employees at colleges, universities and other private education providers. Such jobs have grown 7.5 percent since June 2009. Public school teachers and administrators are counted among local government employees.