Section 25A. The commissioner of insurance shall provide by regulation for an annual report to be filed by each insurer writing workers' compensation insurance in the commonwealth. Such regulations shall require the reporting of litigation expenses incurred by insurers, including the payments made for claimants' attorneys' fees, defense counsel fees, medical testimony, and any other information deemed relevant by the commissioner. Insurers shall also be required to specify the number of claims and portion of their indemnity benefits paid out periodically, and the number of claims and portion of indemnity benefits paid out as lump sum settlements. The commissioner shall also order the rating bureau created under the provisions of section eight E of chapter twenty-six to perform closed claim studies regarding losses and expenses related to vocational rehabilitation, physical therapy, chiropractic services, safety programs or such other matters as he deems appropriate.