Demand for U.S. industrial distribution centers, larger than 300,000 square feet, is high and rising, according to real estate services firm Jones Lang LaSalle's first "Big Box Velocity Index". Improving economic conditions, the continuing growth of e-commerce and a deep bench of tenants seeking space have all created this highly competitive fight for industrial and warehousing space. As a result, there is 96.7 million square feet of industrial construction under way, with nearly half speculative, with an average building size of 360,000 square feet.