Obamacare’s second biggest flaw is that even as it upended the half-century long consensus over who should be in Medicaid, the law inexplicably left intact a feature of Medicaid that we have known for decades fuels excess spending: its open-ended matching rate.

So long as states put up a dollar to fund Medicaid, Uncle Sam is obliged to match it with anywhere from $1 to $3 federal dollars depending on that state’s unique matching rate. It has been proven empirically that this formula fuels higher spending. An analysis by Thad Kousser at UC Berkeley showed that all other things being equal, shifting a state from the lowest to highest federal matching rate increases discretionary Medicaid expenditures by 22 percent.

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