Are we seeing skill mismatch after all?

Peter Orszag writes:

An odd puzzle is taking shape in the labor market: Over the past three years, the number of job openings has risen almost 50 percent, but actual hiring has gone up by less than 5 percent. Companies are advertising a lot more jobs, in other words, but not filling them.

To get some sense of how significant this is, consider that if, since June 2010, hiring had risen a third as much as advertised jobs have (rather than only a 10th), and nothing else were different, job creation would be roughly 500,000 higher each month, and the unemployment rate would already be back to normal levels.

One possibility is that companies are offering jobs, but at wages too low to attract takers:

Some support for this perspective comes from experimental data in the jobs survey, which show that the job-offer rate has risen most sharply (relative to hiring) for establishments with 10 to 250 workers.

Alternatively, companies may be filling positions internally, or they may be advertising without much intention of hiring.  Or we are back to the skills mismatch hypothesis.  Are companies simply expecting too much perfection in their new hires?  If so, why has the demand for (near) perfection gone up?

Here is commentary from Reihan.  And here is commentary by Ashok Rao (did you know he is 18 years old and from Chennai?).