When I started this project, I thought it would be pretty straightforward to develop an automated means of computing how many people in a society could make a pie a week. Instead, this lead to a long and occasionally heated discussion about what exactly constituted "pie", how much work really goes into making one, and whether or not the data for such a thing exists.
About the same time, I stumbled across Dr. Easterly's Reinventing Foreign Aid, which is to econometrics what Michael Pollan's In Defense of Food is to nutrition science. It's not a refutation, exactly, but a serious study of both the assumptions and practice of analyzing complex systems. Meanwhile, a global financial crisis was busy re-ordering the world's economy and making a lot of econometric data about incomes, trade and production obsolete. Meanwhile, serious economists are asking questions of their own field about the validity of counterfactuals and ex post storytelling.
What I've learned from this is not to reject all economic measures outright, but to be very careful to keep the metrics as simple as possible and with very clear ties to the hypothetical narrative. If the story I'm trying to tell is wrong, then my metrics are suspect. If my metrics do not reflect what is actually happening in the world, then my narrative may be wrong as well. In this sense, it is possible to develop metrics that can serve as an aid to examine potential policy options, but they are only as useful as the assumptions underlying their basic narrative. For more on this epistemological approach, see Nassim Taleb's body of work. In short, a simple metric with few assumptions helps inform discussions of the impact of political and personal decisions, while complex models often contain hidden assumptions that make them dangerous to use.
The title of this post has nothing to do with epistemology, but I wanted to be sure I including that disclaimer at the beginning. Now, on to the narrative and its metric:
Narrative (aka hypothesis): The physical pie making capacity in a nation (P-PMCN) depends primarily on its internal food production. This is a mildly controversial statement, since a globalized world can, in theory, rapidly move food from where is it efficiently produced to where it is desperately needed. However, this assumes a much freer market for food than actually exists, and that someone will always be willing to pay to feed foreigners. Because these assumptions are specious, and because the countries doing the best job of providing food security are the ones that ignore classical economic analysis, while those that tried to follow "free market" advice have relied heavily on food aid. This makes my job easier, because food production numbers for a given region are pretty easy to find, and all evidence suggests that a country will feed its citizens first, regardless of their economic position.
So, how to compute P-PMCN? The answer, I think, is to find the limiting factor in a given national production system. To make a pie each week, one needs:
(1) Roughly 2000 Calories/day of food, consisting of .84kg of grains (assuming 70% of harvested grain becomes edible) and .053kg of proteins (active, 180lb young male). Suggestions for improving this "basic diet" model are welcome, please leave a comment.
(2) Enough fruit to make the filling. My pies generally use about 1-2kg (2-4lb) of fruit each, but I'll assume that an even 3kg (6.6lb) are required to allow for losses in travel and "sampling" by the pie maker and family. I don't plan to make any distinction between the types of filling, but this may change with time.
(3) Sufficient fuel to bake the pie. I have used a shovel and backhoe as cooking implements in the past, so I'm comfortable saying that the only thing you need for pie production is heat. For now I will assume this means either natural gas or electricity, and for the developed countries I'll assume that it comes from either natural gas not used for electricity or electric power at 80% efficiency. Further, I'll assume that a pie must be baked at 205C (400F) for 1hr, and that its internal temperature must be raised from room temperature at 25C (77F) to 100C (212F) to bring the fruit to a boil. Assuming 3kg of fruit, which is mostly water, this "internal heat" requirement comes to 941kJ (892BTU), which is to approximately .89 cubic feet of natural gas or .33kWh of electricity. Simply keeping the oven hot for that long consumes roughly 2.5kWh (8530BTU, 8.3 cubic feet of methane). I'd like to independently confirm those numbers, sources and suggestions appreciated.
For the US, we'll use the USDA numbers for wheat, corn and rice production provides a good estimate of the grain available to the population. Using the assumptions above, the US produces about 409billion kg of grain per year, enough to feed 1.3 billion people (roughly 4x the population). Protein production from beef, chicken, pork and cheese comes to 49billion kg, enough to meet the needs of 2.5billion people. P-PMCN is not limited by basic food production in the US, at least as long as the fertilizer, soil and irrigation systems hold out.
Fruit crops are probably also overabundant, although the statistics for them aren't as current in terms of raw production (I welcome alternative sources). However, given that fruit production is largely concentrated in central California, it's availability nationwide depends on keeping transportation costs low.
In terms of energy production, it's important to remember that the US does produce a lot of its own fuel. However, it also uses quite a lot of that fuel for transportation, air conditioning and lighting. What I plan to do is grab the numbers for those three items and subtract them from gross energy production to compute the amount of energy left over for pie making. If you have any suggestions about sources and/or methods, please let me know!
