Lately, the slogan "shop local" has become a mantra for supporting small businesses—a sort of cheer for the underdog in a retail climate where giant box stores reign supreme. 

But in a place like Frankfort, shopping local carries a larger meaning than simply keeping money and jobs in the village. It affects the bottom line. 

Conventional wisdom is that most municipalities' biggest revenue stream comes from property tax, but not in Frankfort.

"Since development has changed, sales tax is the No. 1 revenue stream (for Frankfort)," Village Administrator Jerry Ducay said.

At last week's Village Board meeting, Ducay and Mayor Jim Holland emphasized the importance of sales tax revenue to Frankfort. They encouraged residents to shop at village retailers during the holiday season, highlighting Friday's Midnight Madness event as good opportunity to do that.  Holland also bragged that the village has the lowest rate in the area—7 percent, as compared to 9.25 percent in nearby Orland Park.

Historically, because of holiday shopping, December is one of the village's biggest months in sales tax earnings.

But Ducay is quick to point out that there are too many economic variables to be able to definitively gauge the reasons why certain months pull in more sales tax revenue than others.

"There's an instability to sales tax as a revenue stream," he said, adding that "weird economic spikes" and other outside factors can effect consumer buying habits.

Ducay points to July 2009's monthly sales tax revenue as an example. He credits the national Car Allowance Rebate System—or "Cash for Clunkers"—for creating that month's big spike. But even that is just a guess, he admits.

This variability coupled with Frankfort's reliance on sales tax is why the village is very careful when it comes to setting budget numbers for that revenue stream.

"A lot of why (the village) makes budget is because it budgets conservatively," Ducay said. "It's designed to hit that baseline."

AREA SALES TAX RATES

• Frankfort: 7 percent
• Mokena: 7.5 percent
• New Lenox: 8 percent
• Joliet: 8.25 percent
• Matteson: 8.5 percent
• Tinley Park: 8.5 percent
• Orland Park: 9.25 percent

FRANKFORT SALES TAX REVENUE

Bolded amounts indicate the month that generated the most sales tax revenue each year.