The national vacancy rate for retail real estate in the U.S. edged down to 5.9% in the fourth quarter of 2015 after logging a healthy 20 million square feet of net absorption and setting the stage for rent growth in a growing number of shopping districts in the coming year. Meanwhile only 12 million square feet of new retail space came online in the final quarter of 2015, culminating a moderated pace of shopping center construction last year.