The industry is absolutely inefficient when you consider what inputs required: pesticides, seed, machinery, fossil fuels for planting/harvesting/transport, massive government subsidies -- not to mention the depletion of the soils that come along with it. It is not even monetarily efficient: take for example the dumping of millions of gallons of milk to match quotas this past year. It's far from efficient.

I would not consider something that requires so much input to be "more efficient at feeding a person". It is however a system that is efficient at feeding mass amounts of people -- if you ignore the inputs.

We created Permapeople alongside the principles of permaculture. The efficiency you can create by designing systems that require few outside inputs is unmatched! While the output is not as far-reaching as industrial production, in the hands of enough local folks, growing in their yards, this maximized efficiency of land could technically provide a LOT of food.

PS: growing potatoes is probably easier than you think. One could grow potatoes with very little time and no monetary input.