If we consider “modern browsers” to be IE8, Firefox (all versions), Safari (all) and Chrome (all) and Opera (throw ’em a bone), then overall in 2009, the market share for modern browsers increased from 29.5% to 57.0% — nearly double. This is great news: a real majority of web users are now using very capable browsers.
Approximately 20 percentage points of the increase are attributable to IE8 — it went from around 1% to around 21% during the year. 3 percentage points are attributable to Firefox, 3 to Chrome, 1 to Safari, and then some rounding errors.
The problematic IE6 lost 13 percentage points, or around 38% of its user base.
In December, IE 6 continued its loss of around 1 percentage point per month. The sum of IE7’s and IE8’s market share has remained the same, so overall IE has lost 1 percentage point, all due to IE6.* This means that IE6 users are not upgrading to more current IE versions — they are moving to other browsers. IE8 took about 1 1⁄2 percentage points from IE7.
Chrome gained 0.7 percentage points in December — given its small base, this represents an 18% increase in the number of Chrome users in a single month. That’s a lot.
Firefox actually trended down slightly in December. My prediction of a Firefox plateau may turn out to be true.