One of your footnotes says: if there are ~200 countries in the world then there are ~4000 pairs of countries, and usually the great majority of those pairs of countries are not at war.
If there are 200 countries then there are about 20000 pairs of countries, not 4000.
Less pedantically, I’m not sure this observation is actually evidence favouring the book’s thesis. You say that 68% of pairs of countries have negative expected utility from going to war. Or, to put it differently, nearly 1⁄3 of pairs of countries have positive expected utility from going to war. And yet, as you observe, the vast majority of pairs of countries are not at war.
The main thing this suggests to me is that very little of the not-war in the world is explained by negative expected utility.
Purely pedantic correction:
One of your footnotes says: if there are ~200 countries in the world then there are ~4000 pairs of countries, and usually the great majority of those pairs of countries are not at war.
If there are 200 countries then there are about 20000 pairs of countries, not 4000.
Less pedantically, I’m not sure this observation is actually evidence favouring the book’s thesis. You say that 68% of pairs of countries have negative expected utility from going to war. Or, to put it differently, nearly 1⁄3 of pairs of countries have positive expected utility from going to war. And yet, as you observe, the vast majority of pairs of countries are not at war.
The main thing this suggests to me is that very little of the not-war in the world is explained by negative expected utility.