Oh, and see the following stats for the past 3 months (US only), which shows the #1 most used size in the US is still 1024x768 as of May 2013.
Desktop Screen Resolution (USA, last 3 months -- does NOT include mobile browsers)
http://gs.statcounter.com/#resolutio...303-201305-bar
(takes a while to compute stats and load)
For desktops, screen resolution does not equal browsers size. Very large screen widths (like 2000+) are probably dual monitors, and people with very wide screens do not usually open their browser full-screen.
You can probably find totally different stats on other websites.. It all depends on the type of website and the parameters (desktop, mobile, country, etc).