Though the consumer PC market may be in the doldrums, you can't pin the blame on the iPad, at least according to the folks at research firm NPD Group.

Many analysts have attributed the latest slump in portable PC sales to cannibalization by the iPad, claiming that consumers are opting for the popular tablet instead of buying notebooks and Netbooks. But in a report issued yesterday, NPD's Stephen Baker disagrees, saying that the rate of cannibalization has actually dropped in recent months.

Surveying Apple iPad owners in March, NPD's "Apple iPad Owner Study II" report found that only 14 percent of early iPad buyers (those who've owned one six months or more) chose an iPad instead of a PC. And over the recent holiday season, that number dropped to 12 percent, according to Baker.

Looking further, the cannibalization of Netbooks by the iPad has actually fallen by 50 percent among recent iPad buyers compared with the earlier adopters. Overall, more than 75 percent of the people polled said they bought an iPad without any intention of buying anything else.

So if the iPad isn't the culprit, what's to blame for the downturn in PC sales Baker looks a bit farther back in time.

"The explosion of computer sales when Windows 7 launched, as well as the huge increase in Netbook sales at that time, are much more to blame for weak consumer PC sales growth than the iPad," Baker said in a statement. "Overall it appears that the vast majority of iPad purchases to-date have been incremental to the consumer technology industry."

Windows 7 went on sale in the fall of 2009, by which point Netbook sales had been surging for months. Apple's iPad first arrived in consumers hands in April 2010--and immediately became a hot seller.

In fact, it's been the higher-priced notebooks more than their less-expensive cousins that have taken the biggest hit. NPD's Retail Tracking Service found that sales of notebooks under $500 actually grew by 21 percent over the six months that ended in March.

"The conventional wisdom that says tablet sales are eating into low-priced notebooks is most assuredly incorrect," said Baker. "The over $500 Windows consumer notebooks market is where PC sales have been impacted the most, with a 25 percent decline from October 2010 to March 2011."