Fifty percent of the staff members who work in House members' Capitol Hill offices have been on the job for a year or less, reflecting an overall decline in staff tenure in the last three years, according to a survey released yesterday.

The Congressional Management Foundation, a nonprofit management consulting firm, had no explanation for the decline but noted that average salaries of House staff members in Washington lag about $7,000 behind those of white-collar federal employees here.

The average salary for House staff members was $32,297. Federal employees who work in executive departments and agencies here make an average of $39,472.

As the longevity of staff declines, "you have people who are the prime advisers to members of Congress who have been around for only one session," said Richard Shapiro, executive director of the foundation. "Their perspective is very limited."

The foundation did not survey any of the House committees, where many of the most senior and highly paid staff members work.

House staff members are not covered under most laws that apply to federal employees in the executive or judicial branches.

Each House member is given an annual $441,120 budget for salaries and benefits for personal office staff. Members can hire as many as 18 full-time and four part-time staff members to work in their Washington and district offices.

Members can juggle the budget to pay fewer people higher salaries if they wish.

As of Oct. 1, House members were required to pay employees the minimum wage of $3.85 per hour. There is a salary ceiling of $90,804.

On Sunday, the House voted to cut the House administrative budget by $16 million, effectively defeating a measure that would have increased members' staff budgets by $50,000 a year.

The foundation sent surveys to the personal offices of 435 House members and received responses from 215, or 49 percent.

The responses indicate that House aides stayed on the job an average of 2.9 years, compared to 3.4 years in 1987, a 15 percent decline.

Fifty-two percent of the legislative assistants, 39 percent of the legislative directors and 31 percent of the administrative assistants have been on the job for one year or less. The average age of people in these positions is 26, 32 and 38, respectively.

Shapiro said many members of Congress do not have the necessary management skills to retain staff without raising their pay. Others would rather replace an experienced aide looking for a salary increase with a novice willing to work for less. "What I don't think is understood is the price they pay in turnover," said Shapiro.

The survey found that black House staff members receive 89 percent of the pay of their white counterparts and make up 9.4 percent of the total staff. Nationally, black civilian workers make an average of 77 percent of the salary of white workers and account for 10.8 percent of the work force.

Female staff members make 81 percent of the pay of male House staff.

The foundation found that educational achievement was related to job position and salary. House staff members with law degrees make $18,000 more than those with only bachelor's degrees. Staff members with doctorate degrees make an average of $48,530 a year -- $20,473 more than those with bachelor's.