In the case of any taxable year beginning after December 31, 1970, the provisions of this subsection shall also apply in all respects to a company which writes lease guaranty insurance or insurance on obligations the interest on which is excludable from gross income under section
103. In applying this subsection to such a company, any reference to mortgage guaranty insurance contained in this section shall be deemed to be a reference also to lease guaranty insurance and to insurance on obligations the interest on which is excludable from gross income under section
103; and in the case of insurance on obligations the interest on which is excludable from gross income under section
103, the references in paragraph (1) to “losses resulting from adverse economic cycles” include losses from declining revenues related to such obligations (as well as losses resulting from adverse economic cycles), and the time specified in subparagraph (A) of paragraph (5) shall be the twentieth preceding taxable year.