Nearly 70% of active mutual fund managers beat their standard benchmark, the Standard & Poors 500 index, during the second quarter, according to a report by Morgan Stanley Dean Witter. The market broadened between the first and second quarters and the S&Ps performance return of 6.9% as of June 30 was no longer concentrated in a few stocks, according to the report. In the second quarter, 73 stocks accounted for total performance of the index, compared with 18 stocks in the first quarter. In a significant change from recent years, the smallest 100 stocks in the index were up 26.5%, with the largest 100 stocks in the index posting only a 5.2% return. The best-performing stock in the index was National Semiconductor, up more than 170% for the quarter, but the company carries a weight of less than 0.1% in the index.