IPhone fever is not just an adult affliction. It has trickled down to the younger population as well. Forty percent of U.S. teenagers now own an iPhone, according to a new survey of 7,700 teens by Piper Jaffray & Co. And the ranks of these young iPhone owners are growing rapidly. Back in the spring of 2011 only 17% of teens said they owned an iPhone. By the fall of 2011 that number had grown to 23%. In the spring of 2012, just six months ago, the number was at 34%. "We are reaffirmed that Apple remains the preeminent technology brand for teens," Gene Munster, a senior research analyst at Piper Jaffray, wrote in the report. Before you get all self-righteous about how spoiled kids are today, consider that the report does not get into what generation iPhone teens are most likely to have -- and that makes a big difference price-wise. Now that the iPhone 5 has come out, you can find an iPhone 4S for about $100 and some deals offer an iPhone 4 for free. There's also a good chance that many of these teenagers are carrying around Mom and Dad's old iPhone hand-me-down. Passing along a working but outdated iPhone to a teenager is the perfect justification for a parent to go out and get a new phone. Piper Jaffray also found that the number of teens who own a tablet computer has jumped from 34% in spring 2012 to 44% in fall 2012 -- and 72% of those who do own a tablet own an iPad. You can bet that number will go up when/if Apple releases the heavily rumored iPad mini that is expected to cost $299. "Overall, we expect Apple devices to continue to expand in teen ownership, and we believe the company is set up well to benefit from loyalty among its younger user base," Munster wrote. Indeed. Latest iPad mini rumor: It will be Wi-Fi only PC shipments set to decline for first time in 11 years