San Francisco likely now boasts the tightest retail market in the country, according to DTZ Retail, which reports that the city’s retail vacancy rate dropped to 3.1 percent in the fourth quarter of 2014. For triple-net leased space, asking rents are averaging $59.29 per square foot. In some areas of the city, however, asking rates are as high as $500 per square foot. Read the GlobeSt.com story here