THE NEXT TIME you apply for a credit card, a car loan or a mortgage, a three-digit number will determine whether your would-be lender will give you a sweet interest rate — or point you to the door. That number, of course, is your credit score, and three big national credit ratings agencies keep the files on you that factor into it. Lots of them. The ratings agencies take in updates on more than 1.3 billion credit accounts across the country every month. And, the Federal Trade Commission (FTC) just found, mistakes happen.

FTC investigators determined that at least a fifth of consumers have a material error on at least one of their credit reports, and at least 13 percent have one that affected their credit score. For at least 5 percent of consumers, fixing the problem would nudge them into a more favorable risk category, making it easier to open new credit lines and to secure more favorable interest rates.

The industry argues the numbers show their files are generally very accurate. Critics say they are evidence of an indefensibly sloppy industry happy to rake in $4 billion a year while investing too little in preventing or fixing inaccuracies, with sometimes massive consequences for those burdened by an unfair credit report.

The reality is that the ratings agencies can and do take on many — but not all — complaints. The FTC found that they modified the files of 79 percent of consumers who filed disputes. But it did not try to determine which of those consumers who got no modification or only partial modification deserved more consideration. Post business columnist Michelle Singletary points out, even a small-sounding error rate multiplies out to millions of Americans affected. For them, the stakes are high; the error rate must drop, and dispute resolution must also improve.

More worker training and better systems to move supporting documents between those involved in a dispute would help. The industry insists that it is investing in both. But it shouldn’t stop there — how about random audits of consumer files? The industry claims that there’s only so much they can do when creditors submit bad information about consumers. But it can at least limit the mistakes for which it is directly responsible and find better ways to arbitrate when consumers and lenders make contrary claims. Federal rules, in fact, oblige it to.

As the FTC’s report shows, the government has started keeping closer track of the ratings agencies. The Consumer Financial Protection Bureau, too, recently began monitoring them and the creditors who fill their files with information on their customers. The agencies’ work should help the public monitor the progress — or lack thereof — from here.