Investors are filing fewer class suits involving registration and offering fraud in federal court following a 2018 U.S. Supreme Court decision, a new report says.

Almost twice as many suits have been filed in state courts as federal courts since the decision allowing state court jurisdiction came down, according to a July 31 report from Cornerstone Research and the Stanford Law School Securities Class Action Overall Clearinghouse. The report examined securities class action trends for the first half of 2019.

Investors have pursued 26 state-court-only suits so far, the report said. Another 23 disputes involve both state and federal court...