One of the more curious aspects of American democracy is that it is literally unconstitutional for states to adopt the same system of government as the nation as a whole. In the case of Reynolds v. Sims in 1964, the Supreme Court ruled that all state legislature districts have to have roughly equal populations, because the Equal Protection Clause of the 14th Amendment enshrines a principle of "one man, one vote." That means that an institution like the US Senate, with wildly unequal populations in its various "districts," cannot exist at the state level — at least not anymore.

The rapid changes Reynolds imposed on the structure of many state governments gives us an interesting opportunity to study what kinds of changes we might expect were the US Senate ever to be replaced with a more representative institution (or abolished outright). The evidence suggests that the malapportionment of the Senate is, in fact, a big deal that probably leads the federal government to spend substantially more in places like Wyoming and Vermont and substantially less in places like California and Texas than would otherwise be the case.

Fifty years ago, state legislatures were wildly disproportional

Before Reynolds, state legislative districts were often wildly unequal. The late Rep. Mo Udall (D-AZ) compiled a few of the worst cases shortly after Reynolds came down:

— In Connecticut one House district has 191 people; another, 81,000. — In New Hampshire one township with 3 (three!) people has a state assemblyman; this is the same representation given another district with 3,244. The vote of a resident of the first town is 108,000 percent more powerful at the Capitol. — In Utah the smallest district has 164 people, the largest 32,280 (28 times the population of the other). But each has one vote in the House. — In Vermont the smallest district has 36 people, the largest 35,000 a ratio of almost 1,000 to 1.

Then, overnight, all these states had to correct those huge inequities. One would expect that change to have a big impact on state policy, and an old-to-the-world but new-to-me paper by political scientists Steve Ansolabehere (then at MIT, now at Harvard), Yale's Alan Gerber, and Jim Snyder (then at MIT, now at Harvard) confirms that it did.

The researchers track how state transfers to local governments changed after legislative districts were equalized. They confirmed previous findings that the overall level of spending didn't increase much. But the distribution of spending definitely did:

In the most underrepresented counties … equal votes increased state revenues by $90 per person per year. In the most overrepresented counties, equalization of state legislative populations reduced revenues transferred from the state by $270 per person per year. The cumulative effect was to shift approximately $7 billion annually toward counties that had been underrepresented prior to the imposition of one-person, one vote.

You can also see this in the charts that Ansolabehere, Gerber, and Snyder produce comparing how disproportionately high/low representation was in a given country — as measured by something they call the relative representation index (RRI) — to the share of funds going to that county. The left chart compares per-county spending to representation in 1960; the right compared per-county spending in 1980 to 1960-level representational disparities (since by 1980 those disparities were almost all gone). The relationship, over those 20 years, becomes substantially weaker:

One caveat is that this reallocation appears to have not happened for certain kinds of spending, like highways, that persist for long periods of time. In a paper this year, Stanford's Simon Ejdemyr and Clayton Nall and Michigan's Zachary O'Keeffe found that highway spending in 2002 was higher in counties that had more representation in 1960. "Bridges, dams, levees, subway lines, military bases, and highways are expected to last well beyond the political careers of the politicians who support them," the authors note. They need to be maintained well into the future, which entails more spending decades later. That said, the authors find that spending in other areas (education and welfare, for example) equalized across counties, just as Ansolabehere et al. concluded. Representation still matters.

Of course, the US Senate still has the kind of inequities that used to plague state legislatures. Wyoming's voters have about 66 times as much say in the Senate as California's voters. What this research implies is that if the Senate were suddenly abolished, or if it became proportional, like the US House, there'd be a big transfer of resources from tiny rural states that currently wield far too much power in the body to big, urban states that are currently getting screwed. And given that those big, urban states tend to be more diverse than the tiny rural states, the shift would be a win for racial equality as well.

Thanks to Sean McElwee for the pointer.