Thanks for writing this! I found it a really interesting series and kudos to you for sharing earlier-stage thinking publicly. I definitely know that I can find sharing such thinking pretty daunting!
Small point:
>ACE estimates that the average vegetarian stays vegetarian for 3.9-7.2 years, implying a five-year dropout rate of 53%-77%.
I think that 3.9-7.2 is their estimate for (i) the averagevegetarian adherence length, but you might be interpreting that here as more like (ii) the medianlength of vegetarian adherence?
From that ACE report:
> We can see in the Guesstimate model that after multiplying, the length of adherence for current vegetarians is 32–49 years.
And then they calculate the length for former vegetarians using the following as a basis:
I’d say the underlying distribution here is pretty skewed, so the difference between that average vegetarian length and median vegetarian length might be pretty significant.
So I guess my pretty quick sense is that the median vegetarian adherence length may be a fair bit shorter than 3.9 − 7.2 years. And if you are interpreting that 3.9-7.2 as being more about the median length, and it was in fact a fair bit shorter, then that could meaningfully change some of your conclusions here.
I think that is all somewhat nitpicky though, and I could certainly be wrong about it! Regardless, thanks again for sharing all of this. :)
Thanks Kieren! I was interpreting it to be the expectation of a geometric distribution (i.e. mean length assuming a constant annual probability of leaving), which I think is the correct way to interpret that number? Let me know if that’s wrong though!
The assumption that length is geometrically distributed might not be warranted, I’m not sure.
Thanks, Ben! That all seems fair enough for these purposes.
Fwiw, I think that number might be more the arithmetic mean of some observations. Interpreting it as a geometric mean seems like it doesn’t strongly violate much, but I think the geometric mean is going to be a little bit lower.
But yeah, I doubt it makes much of a difference in the scheme of things!
Thanks for writing this! I found it a really interesting series and kudos to you for sharing earlier-stage thinking publicly. I definitely know that I can find sharing such thinking pretty daunting!
Small point:
>ACE estimates that the average vegetarian stays vegetarian for 3.9-7.2 years, implying a five-year dropout rate of 53%-77%.
I think that 3.9-7.2 is their estimate for (i) the average vegetarian adherence length, but you might be interpreting that here as more like (ii) the median length of vegetarian adherence?
From that ACE report:
> We can see in the Guesstimate model that after multiplying, the length of adherence for current vegetarians is 32–49 years.
And then they calculate the length for former vegetarians using the following as a basis:
I’d say the underlying distribution here is pretty skewed, so the difference between that average vegetarian length and median vegetarian length might be pretty significant.
So I guess my pretty quick sense is that the median vegetarian adherence length may be a fair bit shorter than 3.9 − 7.2 years. And if you are interpreting that 3.9-7.2 as being more about the median length, and it was in fact a fair bit shorter, then that could meaningfully change some of your conclusions here.
I think that is all somewhat nitpicky though, and I could certainly be wrong about it! Regardless, thanks again for sharing all of this. :)
Thanks Kieren! I was interpreting it to be the expectation of a geometric distribution (i.e. mean length assuming a constant annual probability of leaving), which I think is the correct way to interpret that number? Let me know if that’s wrong though!
The assumption that length is geometrically distributed might not be warranted, I’m not sure.
Thanks, Ben! That all seems fair enough for these purposes.
Fwiw, I think that number might be more the arithmetic mean of some observations. Interpreting it as a geometric mean seems like it doesn’t strongly violate much, but I think the geometric mean is going to be a little bit lower.
But yeah, I doubt it makes much of a difference in the scheme of things!
Thanks again for sharing all this :)