Retail sales data shows that Macintosh sales are up 21 percent year over year in October and November and analysts think that December could also be a very strong month.

NPD Group data was acquired by analyst Gene Munster of Piper Jaffray and he believes that Mac sales in the quarter will be between 2.9 million and 3 million. It is however hard to predict as approximately 50 percent of all Mac sales for the quarter will happen in December.

November figures are tied to the new generation of Macintosh computers which were launched and desktop sales were up 74 percent in October and November while mobile systems saw a 5 percent increase.

“While it remains early, it appears the new iMacs are driving Mac sales in the Dec. quarter and we are incrementally more confident in slight unit upside in the Dec. quarter.” said Munster.