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Comment by mustpax | Hacker News Reader

Using the term second derivative obscures the meaning here somewhat. 'Deceleration' would be a more accessible concept to use to describe what's happening. It doesn't mean we're going backwards yet (i.e. net employment gains), but the rate of loss is slowing. At least that's what they told me in Physics class.

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I don't think there's any obscurity; this is high school calculus. If the rate of change (first derivative, negative in this case) is slowing, that means the second derivative is positive here. I'm not yet convinced this is a sign of things to come, however; there are five inflection points in his table where the rate of loss improves.

I'm not saying the terminology is wrong or anything like that. I'm just saying 'deceleration' is a more concise and comprehensible way of talking about changes in the second derivative. You might be surprised how little high school calculus most people have retained.

Or how little high school calculus people have taken. At my high school not even precalculus was a requirement. Of a graduating class of around 300, I'd say 30-45 students had taken a calculus course.

I agree that acceleration would be a much clearer term.

I understood what people meant by "the second derivative" before I'd taken any calculus. It's intuitive; you hear it in context once and you get it.

I think 'deceleration' is more ambiguous.

I tend to think of derivatives taken with respect to time in terms of high school physics.

Let x = postion

x' = velocity

x'' = acceleration

x''' = jerk

(and, incidentally, the 4th through 6th derivatives of position are known, respectively, as 'snap', 'crackle', and 'pop' ;-))

you sir, is a genious.

It might be kind of obscure, but it emphasizes how far we'll go to find good information in a bad enconomy. It's like when people ask you if you know somebody at a party and say "sure, the place belongs to my girlfriend's 2nd best friend's 3rd cousin twice removed" Nobody knows what a 3rd cousin twice removed is, but they know its a long way from being relevant.

Not that this isn't relevant, but it's not an improvement in employment percentage, which is what people who don't need to speculate about the economy really care about.

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