That old numeracy bugaboo
We just keep stumbling over this one.
Look at this headline about Google's archives from the International Newsmedia Marketing Association's weekly news summary:
Now, look at the story it links back to:
It's worth repeating: "Quadruple" does not mean 400 percent growth. It means 300 percent growth. Put another way, while something may be four times as large (or 400 percent of what it was) it is three times (or 300 percent) larger.