The ratio of unemployed to job openings

There are a number of other important labor market charts in David Rosenberg's latest missive over at Gluskin-Sheff, but this is probably the most telling.
Interestingly, the last recession was declared over in late 2001, just after the steepest part of the curve was seen that year. Of course, that call didn't come until almost two years later in July of 2003, the NBER (National Bureau of Economic Research) Business Cycle Dating Committee (all told, that would be NBERBCDC) likely to take at least as long this time around.