Think of the children.

These days, politicians – and their constituents – generally don’t.

  For all their baby-kissing, politicians know that it’s the elderly – not suffrage-ineligible children or their parents – who turn out to vote. This perhaps explains why a smaller and smaller share of government budgets is expected to go to children over the coming decade.

This is documented in exhaustive detail in the Urban Institute’s eighth annual “Kids’ Share” report. The study takes stock of all the different kinds of government spending (including spending through the tax code, such as the child tax credit) that directly benefits children, focusing on the spending controlled at the federal level.

The authors found an uptick in federal spending on children last year, with the share of the budget benefiting the young rising from 9.7 percent in 2012 to 10.2 percent in 2013. But don’t expect the party to last.

Spending on kids as a share of the budget is projected to decline dramatically in the coming decade – to just 7.8 percent by 2024. If you exclude health spending, spending on children falls in raw, inflation-adjusted dollars, too, not just as a percentage of total spending.

 Kids’ share of federal spending isn’t tumbling because children are suddenly becoming a smaller portion of the population. Nor is this happening because we live in an “age of austerity”; the sizes of both the economy and tax revenue are at all-time highs, after accounting for inflation, and are expected to keep growing. Federal spending overall is likewise projected to swell in coming years.

What’s happening is that spending on other stuff – especially the elderly and, even more especially, on health care for the elderly – is crowding it out.

Per capita federal outlays on children rose by about $4,600 in the last half-century (from $270 in 1960 to $4,894 in 2011, after adjusting for inflation); during the same period, per capita outlays on the elderly rose by about $24,000 (from $4,066 to $27,975). The chasm between per capita funding received by seniors – even after taking into account the taxes they have paid – and children looks likely to widen substantially, given the way Social Security, Medicare and child program benefits are structured.

“In essence, we have codified into the law the following rule for the young: They owe us ever more when they become adults, and we owe them ever less while they remain children,” writes C. Eugene Steuerle, one of the Urban Institute report’s co-authors, in his new book “Dead Men Ruling.”

In Steuerle’s view, Americans never deliberately decided to shrink children’s share of the pie; instead, we have been straitjacketed by laws set in motion decades ago by policymakers no longer around to see what fiscal burdens they have wrought. If asked to design a new division of federal spending from scratch, he says, few Americans would come up with today’s system. But taking current policies off autopilot turns out to be difficult politically, since major lobbying efforts protect the biggest beneficiaries.

I agree that this is true at the federal level. But at the state and local levels, which account for the vast majority of spending on children, I worry that more deliberate defunding is on the horizon.

State and local spending on children skidded downward in recent years, falling by about $350 per child between 2008 and 2011 (the most recent year for which data are available). Public education has been particularly hard hit, with the number of people employed in public schools shrinking even as enrollment increased.

Much of this has been caused by shortfalls related to the recent recession. But even when the economy has fully recovered, localities’ commitments to children may waver, particularly as baby boomers age. Research has shown that an increase in the share of elderly residents in a jurisdiction correlates with a significant reduction in educational spending per child.

Bear in mind also that the nation’s oldest and youngest Americans are starting to look more different from one another in ways other than the obvious. Older Americans are predominantly white and were procreated almost exclusively in wedlock; a majority of infants today are racial and ethnic minorities, and they are increasingly born to unwed mothers.

In the generational tug of war over the public purse, it will not surprise me if both sides face mounting trouble empathizing with one another’s economic needs. But one of those groups, politically active as it is, already has the ear of politicians – and existing law on its side.