The record quarterly sales Apple announced Tuesday night were boosted in a big way by repeat customers – existing iPhone owners accounted for 43% of all sales of the new iPhone 4S, according to new research. And many recouped much of the cost by selling their older models.

Only 36% of iPhone 4S buyers switched from a rival smartphone operating system, while 43% upgraded from an older iPhone, according to Consumer Intelligence Research Partners. Among those who bought in the first few weeks after the launch, about 70% were iPhone upgraders, says Michael Levin, a co-founder of the firm. In fact, in October and November, Apple claimed the top three spots among the top 10 smartphone models sold with the 4S, iPhone 4, and 3GS, according to research by the NPD Group, a market research firm. And consumers are clearly willing to play along with the upgrade cycle: About half of new smartphone buyers had owned their previous phone for two years or less, according to NPD Group.
Apple reports its first-quarter earnings tomorrow, and Wall Street’s expecting some record-breaking numbers all around.
Analysts polled by FactSet predict the company will bring in earnings of $10.04 per share and revenue of $38.92 billion. As usual, that’s well above the $9.30 a share on $37 billion Apple forecasted at the end of its last quarter.
There will be a lot to chew on with tomorrow’s numbers, which should come in shortly after the close of trading. But the big one to look at is how many iPhones the company sold.
This is the first quarter to include sales of the iPhone 4S, which hit shelves in mid-October. All indications have been that it’s Apple’s best-selling phone yet, though the company has not provided new data on that since boasting sales of 4 million iPhone 4S units in its first weekend.
Fortune scooped together a collection of 22 estimates from Wall Street analysts, who averaged a guess of 29.74 million iPhones sold. How does that stack up to the same quarter last year? Apple sold 16.24 million units, which in itself was an 86 percent increase year over year. If Apple met the near-30 million estimate for this quarter, that would be about an 83 percent increase this time around.