The ISM PMI's measure the future expansion of economic activity, not the stock market. Benchmarking the PMI's to the S&P 500 is useless because they're both leading indicators...they should be benchmarked against GDP. The PMI's in fact predict GDP 12-18 months in advance with a success rate of about 80%. If you were reasonably certain about GDP's direction 12-18 months into the future would that influence your equity bias? You could make money with this alone by trading the index, but that's not where the juice is...