The American Enterprise Institute and the Brookings Institution, two elite D.C.-based think tanks, teamed up and released a report on paid family leave Tuesday. This follows President Trump's budget, which included a proposal to expand access to paid family leave, and demonstrates that the policy issue is gaining traction.

Rightfully so: As the new report says, changes in labor force participation and family structure have put increasing pressure on dual-earner families (and single parents). When a new child joins a family or when other medical issues come up, workers need to take time off to heal, bond and adjust. And some can't afford to do so.

We should applaud these think tanks for wading into an important and difficult issue area. It is a personal topic, fraught with emotion, as families struggle with juggling work and family life in a variety of different ways. And this struggle obviously affects families of different sizes, ages and income levels differently.

But sadly the AEI/Brookings report comes down on the side of a one-size-fits-all plan, assuming that's what will serve families best.

This is wrong.

Instead, families need flexibility to minimize the downside and maximize the upside of tradeoffs, given their individual circumstances and needs.

The working group behind the report includes economists and thinkers across the political spectrum, and therefore the solution they propose is a compromise, they say. But compromise is tricky. The devil is always in the details.

So what are the details of the AEI/Brookings compromise? Rather than mandating that employers provide paid time off, the group suggests that the federal government fund eight weeks of paid time off for family leave, but only at 70 percent pay and only for people at the lower end of the income spectrum. They suggest funding the budget-neutral plan with payroll taxes and other savings.

Consider what Speaker of the House Paul Ryan once wisely said about compromise: "I'll take an inch where I wanted a mile, but I won't move an inch in the wrong direction."

The compromise proposal in the AEI/Brookings report would be inching in the wrong direction. While a federal entitlement might minimize some of the problems associated with mandating that employers provide paid family leave, it would still come with significant downsides.

A new payroll tax would affect all workers, not just those who would take advantage of the benefit. We ought to ask if that is fair. And the proposal is likely to result in discrimination against women of childbearing age, as employers will (correctly) assume that more women than men will maximize the benefit and miss more work.

Importantly, government intrusion into this issue would stop — or at least slow — the important market-based changes and innovations that could alleviate the problems working families face. Already many employers are moving to create or expand paid time off for family leave. And those who can are offering work-from-home options, flexible hours and other customized leave arrangements to suit their workforce.

Another age-old phrase should be a warning to conservatives: "Give someone an inch, and he'll take a mile." A new federal entitlement to paid family leave will do as all entitlement programs ultimately do: balloon into unsustainable behemoths far beyond what was intended. Eight weeks at 70 percent pay may be an improvement as compared with what some new parents get today, but it will never be enough. We should expect calls to expand the program within minutes of its passage.

We can and should recognize that many families don't have the time and resources they need to deal with new additions, sicknesses or care for elderly family members.

Family leave is a good thing. But when the government gets in the business of trying to provide everyone with good things – like health insurance, for example – our experience should be instructive. "One-size-fits-all" won't fit many.