NEW YORK, AUG. 31 -- The Dow industrial average rose 21 points today in the lightest trading of the year.

Fewer than 100 million shares changed hands on the New York Stock Exchange for the first time in 1990.

NYSE volume, which reached 96.4 million shares, was the lightest since July 6, when 111.7 million shares were traded.

The market showed little direction due to a dearth of consequential news from the Middle East.

Instead, the Dow succumbed to a program-generated whipsaw that transformed an 18-point morning loss into an identical gain by midday.

While the Dow rallied 81 points on the week, 78 points of that gain were made in Monday's session, when a technical reaction and bargain hunting followed the previous Thursday's near-panic sell-off.

Moreover, the Dow this week retraced only 73 percent of the previous week's 111-point slide.

From a longer-term perspective, the Dow has plunged fully 290 points during August, historically a good month for the stock market.

At the close, the Dow stood at 2614.36, up 21.04, while advances outpaced declines by a ratio of 3 to 2. Broad market indexes rose moderately.

Among Dow components there was little in the way of real leadership, tape-watchers said. Merck rose 1 3/8 to 81 5/8 by the close, Exxon firmed 1 to 50, but Goodyear slipped 1 to 22 3/4 and other moves were fractional.

The Dow transports eked a 0.19-point gain from the day, closing at 901.45, but the utility index surged 2.20 to 195.93 despite a small loss in the bond market.

Among broad stock indexes, the Standard & Poor's 500 was up 3.85 at 322.51, the NYSE Composite up 1.60 at 176.83, the Value Line up 0.94 at 247.24, the Amex Market Value up 0.48 at 323.39, and the Nasdaq Composite up 2.53 at 381.21.