The iPhone 4S launch in October was met with high level of demand that has become customary for the launch of new Apple products. Of course, not all of those people lining up for new iPhones are current iPhone users, raising the question of where they all come from.

Consumer Intelligence Research Partners has released a study today that sheds some light on the issue. According to their data, 18% of those who bought the iPhone 4S at its launch in October were switching from other smartphone platforms like BlackBerry and Android. For October, November, and December 2011 combined, that number jumps to 36%.

Additionally, CIRP’s data showed that the iPhone has had a significant impact on the market shares of the major carriers. Three of the four major carriers – AT&T, Verizon, and Sprint – carry the iPhone. The fourth, T-Mobile, does not. CIRP’s data showed that T-Mobile lost market share during the first three months of the iPhone 4S’s availability, while the other three maintained their market share.

Interestingly, the fact that 36% of new iPhone buyers were coming from other platforms seems not to have had much of an impact on those other platforms’ market share. According to an analysis released by StatCounter at the end of 2011, BlackBerry and Android continued fairly steadily in their respective trends throughout the last quarter of 2011. BlackBerry declined steadily throughout 2011, and showed no change in the rate of decline during the three months the iPhone 4S was available. Android, meanwhile, continued its steady climb throughout the year (even surpassing the iPhone in late summer), though it did show a very slight levelling off in October, around the time of the iPhone 4S’s launch.

[Hat tip, AppleInsider]