Congratulations, Bob! 

Thanks for sharing this candid account of your journey, Seth! How fortunate for the HSF Lab that your path landed you with us. Even though the trip was roundabout, it gave you a breadth and depth of skills, and worldliness, that doesn't come rolled up inside a PhD diploma.

Start by doing work you're invested in, that you're proud of, and people may notice.

This is fantastic advice.

Yes, good point

Agreed, though if their model isn't correctly specified to identify the causal effect on meat (which I agree is tough here), then presumably the effects on plant-based sales would also be suspect.

Good point. This does provide a bit more evidence that it's not just due to other January shocks that were happening regularly before Veganuary started.

There's this in the abstract:

"Average weekly unit sales of plant-based products increased significantly (57 %) during the intervention period (incidence rate ratio (IRR) 1·52 (95 % CI1·51, 1·55)). Plant-based product sales decreased post-intervention but remained 15 % higher than pre-intervention (IRR 1·13 (95 % CI 1·12, 1·14)). There was no significant change in meat sales according to time period. The increase in plant-based product sales was greatest at superstores (58 %), especially those located in below average affluence areas (64 %)."

I think this is pretty bad news, actually.

Here we have an intervention that apparently increases sales of plant-based products by 57% and yet does not decrease sales of meat products at all. Unfortunately, this corroborates a growing body of evidence suggesting that plant-based products often fail to displace meat products, even when they gain their own (orthogonal) market share.

As an aside, even with the effects on plant-based products, it's also hard to attribute causation to Veganuary specifically, since it always occurs during a month that we know is associated with unusual recurring "shocks" (e.g., the end of holiday dinner parties; the beginning of New Year's resolutions).

Thanks for putting together this excellent list, Martin and Emma. This is just in time for my lab's upcoming brainstorming session on future research priorities.

No worries. Effect-size conversions are very confusing. Thanks for doing this important project and for the exchange!