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Is growth linear, not exponential?

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Re: Is growth linear, not exponential?

#4

Can’t you model almost anything as a piecewise linear function? I don’t know if this claim is saying much of substance.

Yes, but if your data is actually exponential, the linear segments are not going to be better approximations than an exponential curve. That's what's going on here

Re: Is growth linear, not exponential?

#5

Can’t you model almost anything as a piecewise linear function? I don’t know if this claim is saying much of substance.

Yes, but if your data is actually exponential, the linear segments are not going to be better approximations than an exponential curve. That's what's going on here

True, fair point.

Yeah like the article mentions, they are basically making an analogy to the idea of “punctuated equilibrium” from evolutionary biology. Here’s a good exploration of how punctuated equilibrium works, vs the alternative which is called gradualism.

https://gvpress.com/journals/IJBSBT/vol3_no4/3.pdf

Re: Is growth linear, not exponential?

#6
post #3

Is this new? I remember reading an article a long time ago (maybe 15 years?) discussing how growth in aircraft speed was overall exponential, but linear for each new technology that was introduced.

It would be a change to macro models of economic growth, if accepted. The default is that TFP grows exponentially. There's also a useful comment by Marginal Revolution here (https://marginalrevolution.com/marginalrevolution/2022/04/ad...) where he points out that TFP itself is really just a residual, and perhaps not a very well-defined concept. That is, if you regress

Y = AK^beta L^(1-beta)

with K being the amount of capital and L the amount of labour, A is just the unexplained "scaling factor" and it gets called TFP. But what TFP actually is... is a bit of a whatever-you-like.

Re: Is growth linear, not exponential?

#7

Can’t you model almost anything as a piecewise linear function? I don’t know if this claim is saying much of substance.

Yes, but if your data is actually exponential, the linear segments are not going to be better approximations than an exponential curve. That's what's going on here

If you zoom in far enough every curve looks linear.

Re: Is growth linear, not exponential?

#8

Earlier quoted context omitted.

Yes, but if your data is actually exponential, the linear segments are not going to be better approximations than an exponential curve. That's what's going on here

If you zoom in far enough every curve looks linear.

Not quite! https://en.wikipedia.org/wiki/Weierstrass_function
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