Real property constructed, altered, installed
or improved subsequent to the first day of July 1976, for the purpose
of commercial, business or industrial activity shall be exempt from
taxation, special ad valorem levies and service charges to the extent
hereinafter provided.
Such real property shall be exempt 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 shall be decreased by 5%
each year during such additional period of nine years.