PORTLAND, Ore. ( TheStreet) -- If you build a pop-up shop for costumes and decorations, throw some candy at the kids and get the adults in sexy costumes laden with pop-culture references, is that enough to scare up some Halloween business?In recent years, the retail world hasn't thought so and has been using an increasing array of tricks to get U.S. consumers to buy its treats. Mobile apps are just one tool they use to pry time and cash out of the nation's goodie bags. With other holidays suffering after the recession, retailers need Halloween sales more than ever. According to the folks at market research firm IBISWorld, Halloween spending in the United States is expected to grow to $7.63 billion this year from $7.41 billion in 2010. That's far more than the $5.77 billion U.S. consumers spent on Halloween at the beginning of the recession in 2008, but just less than half of the $13.2 billion spent on Father's Day this year. Halloween ranks dead last behind Christmas ($69.2 billion by IBISWorld estimates), Valentine's Day ($20.8 billion), Mothers Day ($17.1 billion), Fathers Day and Thanksgiving ($7.8 billion). Even with a turbulent economy trimming Turkey Day spending, Halloween's 3% year-over-year growth lags well behind Thanksgiving's 6.4% growth in 2012. Even this year's Halloween uptick is a mixed bag. Spending on decorations is expected to jump 6.7%, to $2.23 billion. Costume spending, however, will increase only by a relatively flat $40 million, or 1.5% from the $2.72 billion spent last year on the holiday's biggest category. Hershey ( HSY) , Tootsie Roll ( TR) , Mondelez ( MDLZ) and other confectioners won't see much of a boost from candy sales, either, as last year's $2.19 billion in spending crawls to $2.25 billion this year -- a change of less than 3%. The news from the National Retail Federation, which represents the nation's retailers and tries to find the positive aspects of even the toughest economic situations, is wearing its gloomiest mask for this Halloween shopping season. The NRF found that 158 million consumers say they plan to celebrate Halloween this year, down from 170 last year. In total, they plan to spend about $75 each on Halloween, down from an average of nearly $80 per shopper last year. Even the NRF's estimated Halloween spending total is relatively modest at $6.1 billion, trailing IBISWorld's figure by more than $1.5 billion. It's not even certain that they'll spend that much, but conservative expectations are rarely exceeded. The NRF places the blame for this year's slump with "cooler fall weather," but political and economic insecurity is a little too scary for consumers and retailers in 2010. Though that NRF Halloween spending estimate is still 54.7% higher than it was in 2005, a quarter of U.S. consumers (25.2%) say the state of the economy will affect their Halloween spending plans. Nearly nine in 10 (86.1%) will spend less overall, up slightly from 83.5% last year. Additionally, 32.7% will buy less candy and 18.1% will make a costume instead of buying one. That affects retailers from Wal-Mart ( WMT) and Target ( TGT) to Kroger ( KR) and Safeway ( SFY). At a time when the balance of Halloween spending is shifting toward adults -- with the $1.2 billion U.S. consumers plan to spend on adult costumes overshadowing the $1 billion they'll spend on kids' outfits -- retailers know their Halloween haul should be much larger. They're just not sure how to capitalize on it. Software developers see it a bit differently. Before mobile devices, Halloween was full of unknowns: People had no idea how many trick-or-treaters to expect, trick-or-treating families had no idea what houses had candy and the only way to know where kids were trick-or-treating for certain was to follow them around. None of that is true anymore, thanks largely to mobile apps.