The S&P 500 stock index, which the Thrift Savings Plan's C fund tracks, suffered a drop of more than 50 points, or 4.92 percent, on Monday, the first day of stock market trading since terrorists destroyed the World Trade Center's twin towers last Tuesday and paralyzed New York's nearby financial district for the remainder of the week. Money allocated to the C fund is invested primarily in the Barclays Equity Index Fund, a stock index fund that tracks the S&P 500 stock index. The Barclays Equity Index Fund, which is designed to track the performance of the S&P 500 index as closely as possible, holds common stocks of all the companies included in the S&P 500 index. Federal investors shouldn't overreact to Monday's plunge, one expert said. "Certainly panic is the last thing one needs," said Thomas Grzymala, president of Alexandria Financial Associates and a certified financial planner. For one thing, TSP accounts are updated monthly, so federal investors should not be as concerned with day-to-day performance as they should be with monthly returns. The TSP is also a tax-deferred retirement savings plan, meaning investors can't withdraw money without a penalty until age 59 and a half. "Most people have quite a long time to go, I don't think there's any need to worry about this today," said Grzymala. In fact, Grzymala said, "millionaires are made in markets like this, particularly in a defined contribution plan like the TSP." Since the S&P 500 was down 53.77 points today investors will be getting a lot more shares for their money. "You can better accumulate wealth in times like this," Grzymala explained. TSP investors need to keep in mind three things, Grzymala said: patience, discipline, and faith in the future. "Particularly now, in these trying times as we defend our liberties, faith in the future is key," he said. Grzymala said none of his 200-plus clients, about 25 of whom are federal employees, called over the weekend in a state of panic about Monday's stock market opening, in which stocks were widely predicted to plummet. TSP investors should remain calm too, he said. "Don't make decisions in haste. This too will pass. Look at any graph of the stock market in the past 20 years. Overall the trend is up and to the right," he said. Beginning Oct. 9, both active duty and reserve members of the military services may enroll in the TSP, with contributions beginning in January 2002.