For instance, TrimTabs.com, a financial research firm, recently reported that margin debt is again in fashion.

Indeed, in 1985, the company made a public offering for the express purpose of using much of the money to pay off margin debt.

Equity is the market value of the stock minus the margin debt.

Known as margin debt, these borrowings had reached historic levels earlier this year.

"And right now the Fed is undergoing a study of margin debt."

But today's level of margin debt is probably not an indication that speculation has returned to the old levels.

In early 2000, margin debt had nearly doubled from a year earlier.

The chief advantage of margin debt, of course, is the interest rate.

Similarly, the amount of margin debt outstanding declined 17 percent in 1991.

From the end of 1989 to early this month, margin debt outstanding soared 22 percent, to $67 billion.