What is PMI (Purchasing Managers Index) anyway? According to Investopedia:
PMI is a very important sentiment reading, not only for manufacturing, but also the economy as a whole. Although U.S. manufacturing is not the huge component of total gross domestic product (GDP) that it once was, this industry is still where recessions tend to begin and end. For this reason, the PMI is very closely watched, setting the tone for the upcoming month and other indicator releases.
The magic number for the PMI is 50. A reading of 50 or higher generally indicates that the industry is expanding. If manufacturing is expanding, the general economy should be doing likewise. As such, it is considered a good indicator of future GDP levels. Many economists will adjust their GDP estimates after reading the PMI report.
Read more: http://www.investopedia.com/university/releases/napm.asp#ixzz22ITKRJ8s