The balance of long margin positions fell below 1 trillion yen for the first time in nearly three years last week, reflecting a wholesale collapse in investor confidence.
The outstanding balance of shares bought on credit stood at 989.17 billion yen at the end of the week, down 57.71 billion yen from a week before, according to industry figures.
The balance has given up nearly 80 percent since it peaked at 4.92 trillion yen in March 2000. Long margin positions last fell short of 1 trillion yen in March 1999.
Information technology issues -- once the high-flying darlings of the stock market -- have taken a battering since spring, leaving investors with huge losses.
With the selling spree spreading across the market in recent months, low- and mid-price "old economy" stocks have also plummeted, setting off demand from stockbrokers for bigger cash deposits from individual investors who borrowed from them to buy stocks.
As the downtrend in share prices continued unabated, many investors were forced to liquidate positions to satisfy the lenders.
By volume, the balance stood at 2.08 billion shares, down 101.99 million shares, the steepest fall since the second week of September.
Stocks showing steep falls in margin buying included Sumitomo Metal Industries, NKK, Nippon Steel and other steel issues.
The balance of shares sold short stood at 1.06 trillion, down 125.34 billion yen.
Some investors, including hedge funds, had been profiting immensely from market declines by short-selling.