A new NY Fed analysis of data from the BLS Job Openings and Labor Turnover Survey (JOLTS) shows that the job-finding rate of the unemployed has been persistently low since the beginning of the Great Recession because the level of vacancies has been low. It's easier to find a job when there are many vacancies per unemployed individuals. Conversely, it's harder to find a job when there a fewer vacancies per unemployed. While the Fed economists who authored the study found that job matching efficiency has been declining since 2005, a relatively low level of vacancies has been the most important factor in the low rate of job-finding since the recession started.
See
http://libertystreeteconomics.newyorkfed.org/2014/02/why-is-the-job-finding-rate-still-low.html