US consumers are starting to change where they shop as their budgets tighten against rising gas and utility costs, and more than one-third plan to spend less on back-to-school items according to two new surveys by market research firm NPD Group.

In its most recent monthly 'Fast Checks Study: Consumers Speak Out on the US Economy,' 34% of consumers in July said they would not change their purchase behaviour - down from April when 42% said they would do nothing different.

"This 8 point drop represents billions of dollars in sales that are not being injected into the normal shopping sectors for consumers," said Marshal Cohen, chief industry analyst at The NPD Group Inc.

Another shift in July was that 41% of consumers said economic conditions would not affect where they shop. In April, that number was 44%.

"This would suggest that we are starting to see signs that consumers are store and channel shifting," said Cohen.

More consumers are also feeling some 'budget erosion' due to gasoline and utility expenses.

In its annual Back-to-School 2008 survey of consumers' purchasing intentions, 35% of consumers told NPD Group they plan to spend less this year, compared to 25% last year.

However, 31% say they intend to spend more this year, down from 36% in 2007.

"The most vulnerable channels of distribution are the apparel and footwear stores," said Cohen.

"Even the discounters will have to work hard to lure customers in to shop. These retailers should expect to see more and more competition from 'non-traditional' rivals like office supply stores."

After school supplies, apparel and footwear are the most popular categories.

"The footwear industry has a way to go to convince parents they need to spend for back-to-school and apparel is right behind with 24% less consumers expected to spend on footwear this year compared to last and apparel showing 10% less spending expected," said Cohen.