Katie Hafner has some interesting stats on Apple’s retail venture. She visited the Apple Store in Midtown Manhattan at 2am and found it humming.

The party inside that store and in 203 other Apple stores around the world is one reason the company’s stock is up nearly 135 percent for the year. By contrast, high-flying Google is up about 52 percent, while the tech-dominated Nasdaq index is up 12 percent.

The popularity of the iPhone and iPod and the intended halo effect those products have had on sales of Apple computers are behind Apple’s vigor. But the company’s success in retailing, as other competitors struggle to eke out sales growth, has been the bonus.

Apple now derives 20 percent of its revenue from its physical stores. And the number is growing. In the fourth quarter in 2007, which ended Sept. 30, Apple reported that the retail stores accounted for $1.25 billion of Apple’s $6.2 billion in revenues, a 42 percent increase over the fourth quarter in 2006.