Consistent economic indexes for the 50 states

"In the late 1980s James Stock and Mark Watson developed for the U.S. economy an alternative coincident index to the one now published by the Conference Board. They used the Kalman filter to estimate a latent dynamic factor for the national economy and designated the common factor as the coincident index. This paper uses the Stock/Watson methodology to estimate a consistent set of coincident indexes for the 50 states. These indexes provide researchers with a comprehensive monthly measure of economic activity that can be used to examine a number of state and regional issues"--Federal Reserve Bank of Philadelphia web site.