As the U.S. economy has improved during the past few years, so has the industrial sector — the warehouses where so much economic activity is housed.

In 2015, the national industrial vacancy rate is set to decline 70 basis points to 6.5 percent, a 15-year low, according to the National Industrial Report from Marcus & Millichap. Absorption is forecast to be 170 million square feet this year, while construction is expected to provide 130 million square feet of new supply, much of it build to suit. The positive supply/demand fundamentals are projected to push up asking rents by 5.3 percent, while fewer concessions mean effective rents also will rise.

The rise of e-commerce has been especially positive for the warehousing sector, as online sales have increased to 11 percent of all retail sales.