ARTICLE SYNOPSIS ...This indicator, a long-term stock market investment tool, compares the performance of the S&P 500 to the New York Stock Exchange index to measure sentiment. The theory is that investors have a preference for certain types of invest-ments, blue chips versus mid-cap, during phases of a bull market. See what this indicator says lies ahead. No financial topic has evoked more interest in recent years than predicting when the current bull market in stocks will end. On one side of the argument are the buy-and-hold adherents, whose methodology has scored remarkable success since the early 1980s. To t...