A study released by the National Ready Mixed Concrete Association points up the growing importance of concrete construction to the national economy. The association's survey of commercial production of ready mixed concrete in 1956 indicates that the industry's total output probable increased by not less than 13%, far outstripping the gain in total dollar volume of construction. The NRMCA findings were based on production statistics covering 1,247 companies out of a total of 2,314 to which questionnaires were sent. Actual production reported amounted to a little over 73 million cubic yards with a total volume of over $962 « million.