Real property constructed, altered, installed or improved
subsequent to March 19, 1984, for the purpose of commercial business
or industrial activity, shall be exempt from taxation, excepting from
this exemption sewer, water, fire, garbage or refuse assessment, together
with any other special district ad valorem levies and service charges.
Such real property shall be exempt, as provided in Subsection A hereof, for a period of one year to the extent of 50% of the increase in assessed value thereof attributable to such construction, alteration, installation or improvement and for an additional period of nine years; provided, however, that the extent of such exemption is decreased by 5% each year during such additional period of nine years.