I've always wondered why it is that going from 3% to 9% wouldn't be an increase of 6% (9-3=6). It seems that when you quote the 300% figure, you're talking about the percent that a percent is changing, but that ought to be a per-decimil rather than per-cent, but people never agree with me on that.

That's where percentage points come in.

hell yes, it 6%, but 200% of 3%(thats %%, or %^2)