There have been more than 200 cases of lost or stolen personal data affecting 8.5 million Americans during the first half of this year, according to a San Diego research group, as a new wave of political and amateur hackers commit data breaches such as last week’s theft of 450,000 e-mail passwords from the Internet content company Yahoo Inc.

The Identity Theft Resource Center, sponsored by technology companies and government agencies, listed 213 cases of data breaches through July 2, suggesting that 2012 won’t show much of an improvement over 2011. Last year, the center tracked 419 cases affecting the personal records of 22.9 million Americans.