There was a 20 percent drop in "help wanted" advertising among 20 of the state of Virginia's newspapers during 1982, according to a study released last week by researchers at the University of Virginia in Charlottesville. Last year was the second year such a drop was documented.

"Help-wanted classified ad lineage is one means of determining the direction of employment trends," said Eleanor May, the director of the survey and a member of the Tayloe Murphy Business Studies Center at the University of Virginia's Colgate Darden Graduate School of Business Administration. May added that because of the types of jobs advertised, "help-wanted ads appear to be a better indicator of white-collar employment demand than blue-collar."

The study showed that the port of Hampton Roads had the greatest decline of help-wanted ad lineage, with a 24 percent drop. Western and central regions of Virginia had the smallest decrease, with a 15 percent drop.

Ads in Northern Virginia were down 23 percent; in Richmond and Petersburg, 21 percent; and 17 percent in the southwestern part of the state.

The researchers noted, however, that the figures for Lynchburg, Roanoke and other southwestern cities may not reflect the full unemployment trend because the region has a high number of blue-collar workers.

The 1982 decreases in want ads followed a 1981 drop for most parts of the state when ad lineage figures declined 21 percent in Northern Virginia but increased 6 percent in the Hampton Roads area.