The credit-card companies' erratic behavior over the past year — slashing credit limits, abruptly canceling accounts, sometimes without even notifying the cardholder — has apparently had a minimal effect on most consumers' credit scores.

That's according to a new study by FICO, the Minneapolis company that calculates the FICO credit score, which is used by banks and other lenders to judge borrowers' trustworthiness.

“Our study suggests that lenders are using a scalpel and not a hatchet to trim their revolving credit exposure and meet their requirements for regulatory capital,” FICO CEO Mark Greene said in a press release.

The study found 33 million U.S. cardholders had their available credit reduced between October 2008 and April 2009. Of those, 24 million had their credit lines cut, despite no new signs of risk during the period.

About 8.5 million people saw their FICO score decrease as a result of shrinking credit limits, while the rest saw no change or actually saw an increase from the cut. The typical score decrease was less than 20 points, the company said.