A company that makes shopping carts for supermarkets and other stores recently purchased some new equipment, installed on each existing machine, that speeds up each machine and as a result reduces the labor content of the jobs needed to produce the shopping carts. Prior to buying the new equipment, the company used four workers and two machines, who produced an average of 80 carts per hour. Workers receive $10 per hour per worker, and machine cost was $20 per hour per machine. With the new equipment, it was possible to transfer two of the workers to another department, and machine cost increased by fifty percent per hour per machine; while output increased by twenty five percent per hour. In both old and new systems, this process operates for 8 hours every day, 7 days a week, 52 weeks a year. What is the percentage improvement in labor productivity as the result of using this new equipment