Last Friday the ISM Manufacturing Index for April was released. It was all but ignored in the economic blogosphere. It shouldn't have been.

Along with auto sales, it is one of the very first economic releases for the month of April. Also crucially, it is a leading economic indicator. The ISM Manufacturing index has typically bottomed a median 2.5 months (a mean of 4) before the end of post WW2 recessions. The latest it bottomed was the month of the end of the recession, the earliest 9 months.

In other words, this is an early indicator with a long and successful track record.

So, why does the NAPM's Manufacturing Index suggest the bottom of the recession is near ...?