WNY index can't keep pace with U.S. economy.(Western New York)(Statistical Data Included)

The third quarter provided additional evidence -- as if any more was needed -- that Western New York has been left behind by. the national economic boom.

The Business First Economic Index, which measures the level of business activity in Erie and Niagara counties, fell 2.1 percent in the third quarter to 1,216 points. It marked the index's fourth decline in the past five quarters.

The nation, as a whole, continued to fare considerably better. The index of leading economic indicators grew-at three times its historic pace between April and August, a sure sign that the national boom will extend into 2000.

The Business First index uses data from eight statistical categories to track economic progress in Erie and Niagara counties. The overall score is tied to a 19 93-95 benchmark of 1,000. Any score above that level indicates that the economy is stronger than it was at mid-decade.

The index's performance …