(a) When another state imposes a tax upon interest earned by its residents on deposits in a lending institution located in this State, but exempts from such taxation deposits by its residents in lending institutions located within that state, then there is hereby levied a tax in the amount of five percent upon interest earned by residents of this State on deposits in lending institutions located in such other state. As used in this section, "lending institution" includes any bank, savings bank, trust company, or building and loan association or other similar institution.

(b) For each taxpayer, $600.00 of income otherwise taxable under this section shall be exempt in each tax year. A husband and wife filing a joint return constitute a single taxpayer. (Added 1977, No. 67.)