I think this part of the article explains much of it.

Older workers, longer time out of work. Shierholz said the exceptionally large number of older workers who are unemployed is also a major factor.

Statistics show it is tougher for anyone (regardless of age) who has been unemployed more than six months to find work.

But Shierholz' analysis of 2009 data shows unemployed people aged 55 and older are about 17% more likely to be out of work for longer than six months than their 25-to-54-year old counterparts.

"Older and more educated people are less likely to become unemployed, but once you become unemployed you're more likely to be unemployed for a long period of time," she said.