Next Time, Follow the Spenders, Not the Talkers
Gretchen Morgenson Market Watch column on future direction of stock market; says investors in stock-index futures have often been correct in predicting market's direction; says in early January 2001, while pundits were pushing stocks, 54 percent of stock-index futures players wagered that stock index would remain in range of plus or minus 10 percent; and 12 percent had made bets that index would fall as much as 25 percent within three months; Standard & Poor's 500 index fell 9.6 percent by end of March; graph (M)