Here is my final word on the demographic impact of the War of the Triple Alliance. Let’s start with the 1899 population pyramid. There is some guess work here, because Asunción accounted for 10% of country’s enumerated population of 480,000 but provided no age breakdown. These figures heroically assume that the capital had the same distribution as the rest of the country, which is almost certainly wrong. (Cities skew older in general; more so in the age before modern urban sanitation.) But the numbers are what we have.
What do they show? Unfortunately, the age groupings make it hard to see whether there are any signs of a general demographic disaster (that is, one affecting both sexes) during or right after the war, but there is nothing particularly obvious. With two exceptions, each cohort looks more or less the size you would expect in a growing mostly-rural population.
The exceptions are the 1854-63 and the 1882-84 birth cohorts. The number of females in the first cohort is slightly smaller than you would expect given the size the cohorts around it. That population was aged 1-10 at the start of the war, so it is possible that we are seeing some effect of disease and malnutrition. The problem is that the cohort after that includes everyone born between 1864 and 1881: war-related mortality among those born in 1864-70 would be swamped by those born in the postwar decade.
The other exception is the 1882-84 birth cohort, which is much bigger than you would expect for both sexes. I suspect that the reason is a head tax on adults or some sort of labor draft that affected both sexes: children who were actually aged older than 18 in 1899 were reported as aged 15-17 instead. (There may be an alternate explanation, but it is unlikely to involve the war.)
What I’ve done here is add back the missing birth cohorts from the 1899 census. The categories did not easily overlap, so I have divided up the cohorts from the 1899 census equally among all the years inside that cohort. (This introduces biases, although I think they run against the hypothesis that the war had no effect.)
Why were the undercounts so large? Well, one possibility is evasion. Another is a sloppy census. But commentator Thomas Masterson hits on a third hypothesis: temporary migration to Argentina. Argentina was booming during the 1880s and getting their from Paraguay was easy. Paraguayan migrants, however, had to compete with the waves of Spaniards and Italians pouring into that country. The Paraguayans would face racial and language discrimination (Guaraní the primary language of most locals at the time), which would not be conducive to permanent settlement. Finally, the 1899 census identified Paraguayans by nationality, not place of birth, and so Paraguayans born in Argentina but who moved back would be counted in the 1899 census as local.
What about the impact of the war? There are clear signs of mass casualties among males: the 1886 male population is a full 41,000 less than might have otherwise been expected ... although that calculation does not account for the fact that male mortality is generally higher than female. Excess male mortality comes to 47% of the population of the relevant age group, which is consistent with the idea that about one out of every two Paraguayan males perished as a result of the war. (It also implies that almost the entire male population served, but that is consistent with Paraguayan records and the overwhelming reports of children and elderly being pressed into service.)
That said, it is a little perplexing that there is also excess male mortality among children born during the war ,i.e., too young to have been child soldiers. There are reasons to think that male children might have been more susceptible to famine and disease, but that smacks a little of post hoc reasoning to me.
Looking at the female half of the distribution, there are some signs of higher-than-expected mortality among the cohorts born during and immediately after the war, but they are not pronounced. Paraguay experienced disease and famine (the latter partially as a result of a huge diminution of the agricultural labor force for military service) but not outside the realm of the historical experience of 19th-century wars.
Finally, it should be noted that even with my adjustments the 1886 number is still an undercount. To be fully consistent with the 1899 number the population would need to grow by 3.0% per year. That is really outside historical experience in the latter 19th century: Costa Rica and the Dominican Republic were the highest (without mass immigration) at around 2.6%. Most countries were around 1.5% or less.
Criticisms, suggestions, new information and additional questions, please! (I know that Randy is interested in why Paraguay survived as an independent nation ...)