In 2010, Congress passed the Fair Sentencing Act, which reduced the vast disparity in the way the federal courts punish crack versus powder cocaine offenses. Instead of treating 100 grams of cocaine the same as 1 gram of crack for sentencing purposes, the law cut the ratio to 18 to 1. Initially, the law applied only to future offenders, but, a year later, the United States Sentencing Commission voted to apply it retroactively. Republicans raged, charging that crime would go up and that prisoners would overwhelm the courts with frivolous demands for sentence reductions. Senator Charles Grassley of Iowa said the commission was pursuing “a liberal agenda at all costs.”

This week, we began to learn that there are no costs, only benefits. According to a preliminary report released by the commission, more than 7,300 federal prisoners have had their sentences shortened under the law. The average reduction is 29 months, meaning that over all, offenders are serving roughly 16,000 years fewer than they otherwise would have. And since the federal government spends about $30,000 per year to house an inmate, this reduction alone is worth nearly half-a-billion dollars — big money for a Bureau of Prisons with a $7 billion budget. In addition, the commission found no significant difference in recidivism rates between those prisoners who were released early and those who served their full sentences.

Federal judges nationwide have long expressed vigorous disagreement with both the sentencing disparity and the mandatory minimum sentences they are forced to impose, both of which have been drivers of our bloated federal prison system. But two bipartisan bills in Congress now propose a cheaper and more humane approach. It would include reducing mandatory minimums, giving judges more flexibility to sentence below those minimums, and making more inmates eligible for reductions to their sentences under the new ratio.

But 18 to 1 is still out of whack. The ratio was always based on faulty science and misguided assumptions, and it still disproportionately punishes blacks, who make up more than 80 percent of those prosecuted for federal crack offenses. The commission and the Obama administration have called for a 1-to-1 ratio. The question is not whether we can afford to do it, but whether we can afford not to.