What is happening is normal turnover in housing, they say.

"I'm absolutely convinced that this would not be happening if there were normal turnover on the court," Professor Merrill said in an interview.

As more people lose their homes, there are fewer people to buy the houses coming on the market through foreclosure and normal turnover, he said.

White House aides call the turnover normal, a result of burnout from 16-hour days and six-day weeks.

The teacher turnover rate has been average the last few years due to teacher retirement, district reductions and normal turnover.

She said that, under normal turnover, about 40 tenants move out of the complex each month.

So if a few uniformed personnel leave, it can be explained as normal turnover.

There is usually an array of units for sale or rent from normal turnover, but right now new developments are generating especially plentiful offerings.

But the former chairman of the seven-member board, who received his removal notice this week, said the replacements went beyond normal turnover.

If there is normal turnover, new vacancies should average about 25 a year, Mr. Kellman said.