Terrorism Risk Insurance Improvement Act of 2007 - Amends the Terrorism Risk Insurance Act of 2002 to revise the definition of "insurer deductible" with respect to a situation where aggregate industry insured losses resulting from a certified act of terrorism exceed $1 billion for an insurer that sustains any of such losses.
Sets forth a calculation for the value of such an insurer's direct earned premiums over the calendar year immediately preceding the program year.