The data breach at Target Corp. that exposed millions of credit card numbers has focused attention on the patchwork of state consumer notification laws and renewed a push for a single national standard.

Most states have laws that require retailers to disclose data breaches, but the laws vary wildly. Consumers in one state might learn immediately that their personal information had been exposed, but that might not happen in another state, and notification requirements for businesses depend on where their customers are located. Attorney General Eric Holder has joined the call for a nationwide notification standard, but divisions persist, making a consensus questionable this year.