As promised, here is how to determine basic percentages. Too many of my college students don't understand basic percentages. Clearly GTF has the same problem. So here is how it works -- in words -- with no math symbols. I'm totally serious. It's never too late to learn. And not knowing how to relate "doubled" and "100% increase" is the mathematically equivalent of being functionally illiterate.
To say how many times something increased, simply divide the second number by the first: There were 10 arrests; now there are 30. 30 divided by 10 is 3. Arrests tripled.
To figure out a percent increase or decrease, subtract the first (earlier) number from the second (later) number and then divide the result by the first number (multiply by 100 -- move the decimal place over two to the right -- to get a percentage).
30 minus 10 is 20; 20 divided by 10 is 2; 2 times 100 is 200. So 30 arrests is a 200 percent increase compared to 10. A 100 percent increase would be the same as saying something doubled.
Going the other way, from 30 to 10 arrests would be one-third as many arrests or a two-thirds decrease or a decrease of 67 percent.
And nothing, not even math skills, can decrease more than 100 percent.
Next I'm going to talk about rates.