With a wholesome smile that lights up her face, Jillian Wagner hands a chocolate ice cream cone to a customer at Heisler's Cloverleaf Dairy in Walker Township.

The 18-year-old Barnesville teen is starting her fourth summer of work at Heisler's, saving most of her earnings to help pay for college in the fall.

"My sister worked here before, and so did my brother, so it's pretty much a family thing," Wagner said. "I'm going to Indiana University of Pennsylvania in the fall, so I'm saving for that, and paying for gas and other things."

Wagner is among the millions of teens working at summer jobs a number that has been falling in fits and starts since 1999.

That year, there were a total of 2,017,000 new summer jobs for teens nationwide. By 2011, that figure had dropped to 1,087,000, a 46 percent tumble, according to employment consulting firm Challenger, Gray & Christmas.

Employment trackers have yet to agree on a reason for the drop.

"While it is logical to assume that the weak economy is the primary contributor to lower teen employment, a closer look at employment statistics reveals that the number of teens opting out of the labor force (meaning they are neither working nor looking for work), has been on the rise since the mid-1990s," Pedderson said. "It is difficult to determine what exactly is driving this trend, but it may be that more teens are using their summers to take more classes, volunteer or attend camps specializing in specific skills or activities, such as a sport, art or science camp. They may be earning some spending money through the odd baby-sitting or lawn-mowing job, but these will mostly fall under the radar of government tracking."

The drop in summer jobs for teens has been across-the-board and very unusual, U.S. Bureau of Labor Statistics economist Teresa L. Morisi wrote in a May 2010 Monthly Labor Review report.

"The recent declines in summer employment rates among teens have been large and unprecedented, and have occurred across all major demographic groups," she wrote. "Several reasons for the declines are related to education.

"First, the proportion of teens enrolled in school during the summer was on an upward trend over the period examined. Second, a number of factors suggest that teenagers are facing greater academic demands and pressures than in the past, which, together with the desire to achieve, may incline them toward placing greater emphasis on academics than on working. Finally, teenagers were affected by the two recessions that occurred during the 2000s, which likely resulted in both reduced job opportunities and increased competition for those jobs which were available," she wrote.

The nadir came in 2010, when only 960,000 new summer jobs were added. It was the "weakest summer teen hiring total in decades," said Challenger, Gray & Christmas spokesman James K. Pedderson.

"At the time, we were just coming out of the worst recession since the Great Depression. States and local governments, which are responsible for a lot of teen hiring through park districts, swimming pools, camps, etc., were making deep cutbacks due to massive budget deficits," he said. "Retailers, restaurants, amusement parks, movie theaters, all of which are major job sources for teens on summer break, were closing or cutting staff. There was also much more competition for jobs from people in their 20s and older who were more willing to take jobs normally filled by teens. Basically, it was a perfect storm of factors that kept teen hiring that year near a record low."

But the numbers appear to be resurging. In May, the first month of the teen hiring season, the numbers of new summer jobs rose to their highest point since 2006, according to Challenger, Gray & Christmas.

"This year, we saw fairly strong gains in employment among 16- to-19-year-olds in May, with nearly 157,000 net new jobs for this age group, Pedderson said.

"In fact, it was the strongest start to the teen summer hiring season since 2006," he said. "However, the overall number of teens working over the summer has fallen significantly since the late 1990s. In 1999, teen employment in July, which represents the peak of teen summer employment, reached 8.75 million. Last year, July employment among teens was slightly under 5.2 million."

For Wagner, who plans to major in communications at IUP, working at Heisler's is rewarding.

"I love scooping ice cream. I love dealing with the customers, and the people I work with are really fun," she said.

Heisler's owner Leonard Ostergaard is proud to be able to provide jobs for teens.

"It helps us to better serve our customers, and it helps the kids because it gives them a job and some income for the summer," he said. "It's good experience for them to deal with the public. For most of them, this is their first job, so it's a good thing."

Apparently, Ostergaard is on the right track.

Michael Saltsman, a Research Fellow at the Washington, D.C., based Employment Policies Institute, said that despite the drop in the numbers of new jobs added, Pennsylvania enjoys a relatively low teen unemployment rate.

Pennsylvania has one of the lower teen unemployment rates in the country. One reason may be the state's numbers of resorts, hotels and parks.

"Pennsylvania has enjoyed steady growth in service-sector employment over the last two years. This is, of course, where a sizable number of teens are employed nearly 40 percent of the state's employed teens worked in leisure and hospitality businesses in 2011," Saltsman said.

Pennsylvania's current teen unemployment rate is 17.3 percent 10.3 percent higher than the unemployment rate as a whole. New Jersey's is 25.6 percent, Ohio's is 18.2, and New York's is 27.5 percent, according to figures released by the Employment Policies Institute.

Nationwide, teen unemployment rates are up almost 25 percent, according to the Institute.

The Pennsylvania Center for Workforce Information and Analysis figures show that last year, 265,200 teens out of a labor force of 314,500 were working at summer jobs. County level data was not available.