According to market research by the Motor & Equipment Manufacturers Association (MEMA), aftermarket activity generally follows a yearly cycle with sales going up in January or February, decreasing in early to late spring and then peaking again in early summer.

The cycle is revealed in MEMA's Aftermarket Activity Index and the Installer Liquidity Index, new features in its bimonthly newsletter, Market Analysis. The aftermarket index tracks overall aftermarket sales and how they are affected by the current economy.

"When the economic picture is looking good, there are typically more sales of both new and used vehicles. This results in greater aftermarket parts sales as used vehicles are upgraded for resale," said MEMA Director of research Frank Hampshire. "When the economy is doing poorly, consumers often hold onto their vehicles longer and have to replace parts as their vehicles age. The aftermarket is not quite as susceptible to changes in the economy as other industries, since people have to drive and repair their vehicles," he said.

MEMA's Aftermarket Activity Index shows that sales activity was fairly low in 1998, a year with a record number of job layoffs and stock market ups and downs.

Another dip occurred in May 2001, followed by major improvement until a sales drop in January 2002. Sales rose at a lower level in 2002 as the economy continued to falter and then fell below average again in September 2002.