Percentages are relative. An increase in the percentage of spam from a certain country does not necessarily equate to an increase in the number of spam messages generated by that country. It could be that other countries are just instituting better controls (and cutting spam). Or even just growing at a slower rate.
Saying that China's share was cut in half is not that significant. How about giving us some actual statistics?
A dramatic rise ?!?! For god sakes, the US is responsible for almost 1/4 of overall spam and now they're worried about the 8% number from Russia.
More, last time i checked the US is a country and not a continent. People, you're not even comparing apples-to-apples here. The american continent, as a whole, is responsible for 38% of overall spaming !