“Regulatory proceedings” and “regulatory investigations” are terms used in the most recent Annual Litigation Trends Survey Report of Fulbright & Jaworski. No distinction is made between them, but one feels adversarial (investigations) whereas the other could be an administrative hearing like a rate increase proceeding.
Sixty percent of their 405 respondents (U.S. and UK) did not have a single regulatory proceeding commenced against them during 2010. That means forty percent did. The next page of the report (pg. 27) states that 55 percent of the U.S. respondents had retained outside counsel during 2010 for assistance in any governmental or regulatory investigation. The two figures mesh reasonably well.