Compiled ByDeborah Austin Board-of-director memberships are shrinking -- but increasingly, firms are relying on board talent for guidance through key business decisions -- says the latest Spencer Stuart Board Index. The analysis of S&P 500 companies -- from consulting firm Spencer Stuart Inc., Chicago -- found a 45% decrease in new-director appointments from 1998 to 2001. From 1990 to 2001 the average board size fell from 15 to 11.1. Early on this trend likely signaled intentional pare downs for efficiency, says the analysis. "Today, it may say more about the difficulty of replacing directors when they depart." Current and retired CEO's -- still the most actively sought group -- comprise 59% of new directors in 2001's analysis. But such executives are becoming more leery of overcommitment. Meanwhile the average number of standing committees per board has remained the same -- four -- indicating that remaining board members are more actively involved. And boards are becoming younger: This year, 60% of members are over the age of 60 -- down from 75%-plus in 1990.