The number of personal bankruptcies increased 34 percent compared with 2001 and have quadrupled in the last eight years.

Partly as a result, the number of miles traveled each year on American roads has quadrupled in the last 40 years.

The American specialty tea market quadrupled in the years from 1993-2008, now being worth $6.8 billion a year.

Current enrollment has quadrupled in the years since the name change and is currently just under 4,000 students.

Use of methylphenidate has actually quadrupled in the last ten years.

Premium imports quadrupled to 400 million in the last five years.

Shares of Genentech have quadrupled in the last two years.

Francisco Recio, director of international programs, said the company's business had quadrupled in the last three years, to 200 patients a month.

About five million students are currently on line, a number projected to quadruple in the next three years.

The zones, whose number has quadrupled in the last eight years, have become popular because of a key trend.