Most people hate those math 'story problems' they always handed out in school, tragically, in real life, story problems are the ones most like what we are required to solve. Same with all the stuff where they wanted you to 'guess' (oh sure they used a fancy word, 'estimate' - but face it, you were guessing). Either way, what they wanted you to do was take the available information and at least string it together in such a fashion that you could arrive at a basic range that the answer would fall into. Sometimes you can bring outside information into it, other times you can't, and you never know all of it, as the wise one once pointed out:
There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know.
—Former United States Secretary of Defense Donald Rumsfeld
So you take numbers you have a familiarity with. Number that are real to you (This is where we lose a lot of people, as they have no real personal association with numbers). And as long as you're at it, might as well take numbers that are easy to work with - hence rounding. I have a couple pretty big numbers in my head. Like: the population of the US = 300 Million, of California, 37Million (roughly 10% of the nation as a whole) and Iowa, 3Million, (so about 1% of the nation). I've been in crowds of 1/4Million, 1/2Million and in Chicago over a million. It's a lot of farking people. People for miles. The rough area I live in has 150K in the city, 450K for the county, and 7.3 million for the region (Bay Area). Those are number's that I 'know' (they are 'known knowns'). I can clearly visualize what it would look like if everyone in my city got up and went downtown. Same for the county. And I can project to the region, I already have a very clear understanding of how much space it takes to house them.
Then you take the definitions - which is just you narrowing or expanding the variables (don't matter which at this point) so I'll use 'irreversible surgical procedure' like many of the state laws do. And then you work the numbers. 1 in 30,000, well hell, we got more than five in Santa Rosa for sure. I know of three I see all the time. That number gets you 10,000 for the country and I think they counted some 8K in the Bay Area some 10 years ago, so there has to be more than 2K elsewhere in LA, and that's not even the rest of the US. So that's not right. Let's slip it down one, 1: 10,000 that get's you to 30K, a somewhat more reasonable number. But we do have some statistical back up. One, there are not that many doctors doing the procedure, its' easy enough to figure how many they can do a year. And we can also look at changes in LS/SS records for gender over a couple of years (I'm sure the number is higher ever year) and get a baseline. Those numbers, of records changes, will generally fit the defination of 'irreversible surgical procedure', and since just about everyone in the US has a DL/State ID (same thing for our purposes), will give us a pretty accurate tally.
