It'd be interesting to see if the initial windmills when introduced were more efficient, post-tax and capex, than traditional methods.
There's a parallel with grains: staples like rice and wheat are more legible to states than other alternatives like legumes, tubers, and starch plants, even though the latter were comparable in terms of calories generated by unit labor. E.g. many roots are buried and hidden from tax collectors. States which enforced cultivation of the legible grains had a greater tax base and outcompeted those that didn't.
That's not very convincing. Before the introduction of the potato, there were no below-ground alternatives that were superior to cereals in Europe and Northern Africa.
> E.g. many roots are buried and hidden from tax collectors.
Those roots tend to be attached to green stuff that's above ground and very visible. Why should that be any less legible to tax collectors than wheat or rice?
> Those roots tend to be attached to green stuff that's above ground and very visible. Why should that be any less legible to tax collectors than wheat or rice?
It's a combination of factors. Cereals like wheat and rice tend to ripen seasonally and simultaneously. They do so visibly, and must be harvested soon after. So a state sends its tax collectors around when the grains are ready to be harvested, and the amount that was generated is immediately visible. They also keep well: tubers go bad relatively quickly (and can be kept underground until actually needed for consumption), while rice and wheat can be transported over long distances and times with an order of magnitude less loss.
Consider the case of the Incas. As a civilization, they relied on two crops for calories and nutrition: maize and potatoes. Despite that, efforts at taxation primarily focused on maize, because it was so much better suited for taxes and commerce (though they did eventually invent a way to freeze dry potatoes).
There's a parallel with grains: staples like rice and wheat are more legible to states than other alternatives like legumes, tubers, and starch plants, even though the latter were comparable in terms of calories generated by unit labor. E.g. many roots are buried and hidden from tax collectors. States which enforced cultivation of the legible grains had a greater tax base and outcompeted those that didn't.