Spring means it’s time for the familiar sights and sounds of professional baseball: meticulously mowed outfields, the crack of a bat against a ball, and bobblehead giveaways.

Baseball teams are out to win games, and they play a staggering number each year when compared to other professional sports. How can they keep fans coming back?

Bobblehead giveaways, it turns out, increase attendance by around 25 percent on weekdays and 9 percent on weekends, Graduate School of Management student Mai Nguyen found.

Nguyen, along with assistant professor Mike Palazzolo and fellow student Jamie Ho, analyzed data from all Major League Baseball games played in 2012 and found an average ticket sales bump of around 4,500 when those wobbly plastic characters were handed out.

“On the other hand, only one team suffered lower attendance at games with the promotion: the San Francisco Giants,” she wrote on the Graduate School of Management website. “The team drew an average of 1,023 fewer fans on bobblehead nights.”

The teams that saw the biggest bobble-benefit were the Los Angeles Dodgers, Toronto Blue Jays and Atlanta Braves.

Read more on the Graduate School of Management website, or see a more in-depth recap where Nguyen included information on how fireworks or cloud cover affect attendance.