The website tracks how often people view and print coupons and their redemption rate. Right now, Coupon.com's Internet Coupon Index, as it's called, shows a spike in coupon offers and demand.
This pattern is almost identical to the one that played out right before the last major economic downturn. The higher the index value, the more consumers are under economic pressure, Boal told CNBC.com.
"The index tends to run in a range," he explained. "In September, October, November in 2007, it popped out of its range for the first time... And, for the first time since then, we are seeing a tripping out of the range," said Boal, a former Wall Street executive.
Boal considers coupons a leading indicator because you don't need months of data to see consumer behavior patterns emerge. He said he expects that payroll tax hikes, rising food and gas prices are squeezing household budgets.
It also helps to look at the types of coupons shoppers are redeeming. The most popular ones right now are for soup, cheese, rice, pasta and M&Ms.
"When people are feeling tightened, they seek comfort food. But also things that make them feel better from personal care and beauty. Dove soap, Pantene and Vidal Sassoon are trending right now," said Boal.
Since the last recession, consumers have really changed their buying patterns, according to Boal. But the behavior Coupons.com is seeing now represents another shift. Those who weren't affected by the last recession are now tightening the reins.
"It indicates to us that people are feeling particularly anxious right now," Boal added. "As we headed into 2013, I really didn't expect this indicator to stand up."
A recent survey from the National Retail Federation showed seven in ten Americans were adjusting their spending plans to cope with this year's payroll tax changes. Nearly half of those polled said they planned to comparison shop more often.
But not everyone believes the consumer is getting overly stressed.
Global Hunter Securities Macro Strategist Richard Hastings said growing labor demand is boosting the mood of consumers.
"In the mind of the consumer, the first priority is job retention and wage continuity. If those are in place, then the consumer will budget to spend, not to retreat, " said Hastings.
-By CNBC's Stephanie Landsman; Follow her on Twitter @StephLandsman.
Questions? Comments? Email us firstname.lastname@example.org.
Strike Three! The American Consumer is Out
Darden Sees Lower Traffic as Consumers Pinched by Economy
Take a Look atThe 40 Most Unusual Economic Indicators:%Gallery-179254%