If your target audience is English-speaking or European countries, the relevant proportion is 2% to 3% or less.
That's a pretty good level to start to consider whether supporting that small percentage is actually making you more money than you would if you didn't support their browser.
The government mandate encouraged many websites to also use ActiveX. South Korea is probably the only country where ActiveX is still in use. Internet Explorer has a browser share of 90-95% in Korea. IE6 is about 15-20% of this.
The sordid history is here! -> http://blog.mozilla.com/gen/2007/02/27/the-cost-of-monocultu...
People don't feel any need to upgrade, as everything works with their current browser/OS.
I've used the internet at my Sister in law's (in Korea) - lightning fast internet speeds, with a creaking slow operating system full of bloatware.