Comment by rossvor | Hacker News Reader

Comment by rossvor | Hacker News Reader

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I guess I see now where confusion point seems for other people.

> If it's per capita, can't you just list every city that has a lower per-capita rate and claim that it is higher than all of them "combined"?

I can't, since that would be wrong, that basically not how I ever read and understand that sentence(if it has "combined" in it), I am not a native english speaker so I'm maybe wrong on this.

Mary gets paid 90k per annum, this is more than what Jane and Jill get per annum combined. I read it as: Mary's per annum (90k) > Jane's per annum + Jill's per annum

Mary gets paid 90k per annum, this is more than what Jane and Jill get per annum. I read it as two separate comparisons: Mary's per annum (90k) > Jane's per annum, Mary's per annum (90k) > Jill's per annum

Salary per annum combines additively, that's fine. £10/yr + £20/yr = £30/yr, easy.

When you add 2 annual salaries you're not increasing the number of years that the salary is paid over.

Death rate per capita does not combine additively, that makes no sense. What would it even mean? 0.1 deaths per capita + 0.2 deaths per capita is not equal to 0.3 deaths per capita because the denominator changes.

Why does the denominator change? You're looking at deaths per 100,000 population, and the 100,000 doesn't change for each city.

You're doing very simple fraction addition: 1/100,000 + 5/100,000 = 6/100,000

The denominator changes because when you look at 2 cities together you don't just add the deaths (numerator), you also add the entire population (denominator).

If there are 100,000 people in city 1, with 5 deaths, and 100,000 people in city 2, with 10 deaths, then we have:

city 1: 5 deaths per 100,000

city 2: 10 deaths per 100,000

Adding them together, we don't get 15 deaths per 100,000! We get 15 deaths per 200,000 (because they each have 100k residents) = 7.5 deaths per 100,000.

I feel like I'm missing the joke here.

EDIT: I mean, yeah, literally, if you add the fractions together, you get what you wrote. But that's not a meaningful way to combine death rates.

Sorry, yes, you're right. I'm being dumb.

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