More consumers are living hand-to-mouth these days, a change that has prompted manufacturers and retailers to shift the timing of monthly sales and promotions.

According to a recent CareerBuilder.com survey, 77% of workers say they are living paycheck-to-paycheck; in other words, their income and expenses leave them little or no savings to fall back on and no opportunities to put aside more. Last year, 60% said they were in such a situation.

Not surprisingly, a freshly-deposited paycheck triggers our impulse to spend.

People are a little less price sensitive, says Arul Mishra, an assistant professor of marketing at the University of Utah who co-authored a recently-published study on the subject. They start thinking of things to buy that will improve their life. That happens regardless of how much money is in their checking account or when they expect another paycheck, she says.

Stores are familiar with this phenomenon. Many retailers see a spike in sales at the beginning and the middle of the month, says Vishal Gaur, an associate professor of operations management at Cornell University. These sales peaks are more pronounced for discretionary items than things people buy throughout the month such as groceries, he says.

With more people waiting for a paycheck to spend, some businesses are adjusting the timing of their offers. For example, retailers are more apt to stock more bulk packages and offer bundled deals at the beginning of the month, and feature smaller sizes and individual-item sales toward the end when budgets are tight, says Wayne Hood, a senior research analyst for BMO Capital Markets. The goal is to sync competitive deals with the moments shoppers are more likely to hit the store.

Groceries, Personal Care and Home Goods

Supermarkets are usually packed on the first few days of the month, and it s no wonder -- there are 191% more coupons at that time than there are mid-month, says Teri Gault, the founder of shopping site The Grocery Game. Procter & Gamble offers a free-standing grocery insert in papers and circulars that week, but there are also more printable coupons on sites such as SmartSource.com and RedPlum.com, she says. The exception: there can be just as many coupons mid-month in anticipation of a major holiday such as Thanksgiving or Easter.

On the weekly sales cycle, wait until Sunday to shop to maximize savings with store sales and the latest round of coupons.

Airfare

Friday paydays don t favor travelers. If you re shopping over the weekend, you re paying too much, says Rick Seaney, the chief executive of airfare price-tracking site FareCompare.com. You want to be shopping Tuesday through Thursday. Fare sales go by a weekly rather than monthly cycle, and that s when prices are at their cheapest on competitive routes.

Autos

Logic tells you that toward the back of the month would be best [for buying], says James Bell, a vice president and executive market analyst for Kelley Blue Book. That s often true, but a dealership that had strong sales may be less willing to negotiate, he says. Shop at the end of the month, but be sure to compare prices at several locations.

Automaker incentives such as cash back or lease deals have a more haphazard monthly cycle. The companies are more concerned with overall sales and inventory, as well as holiday weekends when they can expect more people to visit the lot, Bell says. (This month, for example, deals from Chevy and Honda end the day after Labor Day.)

Clothing

Sales have been fairly constant this year with shoppers cutting back spending, says Howard Davidowitz, the chairman of Davidowitz & Associates, a national retail consulting firm based in New York. Customers can benefit by buying as needed and waiting for price drops instead of stocking up during one big sale.