You should use gross premiums written as the measure of sales in or into the United States for the exemptions in 802.50 and 802.51.
Question
It seems clear from informal interpretations that for insurance companies US revenue for the purpose of the HSR form (former Item 5(a)) are net premiums written (e.g., https://www.ftc.gov/legal-library/browse/hsr-informal-interpretations/1501002). However, I have not located any interpretation on whether net premiums written or gross premiums written are used for the sales in or into the US test for the exemptions in 802.50 and 802.51. Would you please let me know which is the correct measure of sales in or into the US for an insurance company?