Complex sentence: The OMB review process became more formalized in 1981 with President Ronald Reagan's Executive Order 12291, which was in effect from 1981 to September 1993, the Reagan and George H. W. Bush Administrations and the first nine months of the Clinton administration.
Split into simpler sentences: The OMB review process became more formalized in 1981 with President Ronald Reagan's Executive Order 12291, which was in effect from 1981 to September 1993. It continued during the Reagan and George H. W. Bush Administrations and the first nine months of the Clinton administration.