The most popular index which follows U.S. blue chips is the Dow Jones Industrial Average.

Still another popular index is the National Mortgage Contract Rate, or N.M.C.R., the average of market rates across the country.

Yesterday the Dow dropped 237.90 points, dragging the popular index back into minus territory for 1998.

The magazine also published an equally popular index of Computer User Groups and their meeting schedules.

Since 1991, the index has outperformed other popular indexes such as the S&P 500 and Dow Jones Industrial Average by about 10 percent.

The S & P 500, one of the most popular indexes, announced last Wednesday that it was dropping Kmart.

Trading of the popular Standard & Poor's index of 500 stocks was immediately halted on the Chicago Mercantile Exchange.

The problem is more basic: The construction methods for popular indexes can create significant biases.

These are unusually wide gaps between the two most popular and closely watched indexes, which usually move at about the same pace, up or down.

Many popular indices, including Gini index, do not satisfy this property.