Total U.S. spending online decreased only slightly from $4 billion in August to $3.97 billion in September, according to the 21st monthly survey conducted by Forrester Research, Inc. in conjunction with Greenfield Online, Inc.

The number of households shopping online increased to 15.2 million in September from 14.8 million in August. Consumers spent an average of $262 in September, compared with $273 in August.

“The fact that online retail remained stable during a month of such social and economic instability speaks volumes about how well eCommerce is positioned to stand up to a poor economy,” said Christopher M. Kelley, an analyst at Forrester.

To view a chart with historical survey data click here.

Forrester Research, Cambridge, Mass., is an emerging-technology research firm. Greenfield Online, Inc., Wilton, Conn., provides Internet-powered marketing research and real-time business information.

JCK