The first nationwide survey of bounce house injuries has found that the unregulated, inflatable death castles are the site of an epidemic of pain, suffering, and injury on a massive scale not seen since the Great Trampoline Plague of 1985.
Yes, there have been at least 65,000 emergency room visits for kids' moon bounce-related injuries, and a 15x increase between 1990 [!] and 2010. But maybe that's because bouncy equipment is exponentially more common now? As seen by the fact that 55% of all incidents happened between 2006-10? Just wondering?
Anyway, kids under 5 account for 36% of injuries, and those are primarily fall-related. Or collision-related. Or falling out onto the parking lot-related. And they're mostly bruises and broken limbs. So of 2010's 11,000 incidents, 3,958 were under 5yo, and 1,912 were fall-related, and 1,200-something, 75%, were in late Spring/Summer.
Which means they're caused by some combination of overstuffed bouncy castles run by dim bulb teenagers and inattentive parents. Just keep an eye on the kids, keep the shrimps and the teens separated, and figure a broken arm is a small price to pay for growing up in a country free of any meaningful safety regulations or oversight on these things.