The Charleston area's industrial real estate market continued to gain strength during the fourth quarter of 2014, according to a pair of reports issued last week, with one analyst claiming the sector's vacancy rate hit a five-year low during the period. Avison Young, a worldwide commercial real estate firm with an office in Mount Pleasant, said vacancy in the region dipped to 7.5 percent during the last three months of 2014, with annual rents averaging $4.45 per square foot.