The RSM US Middle Market Business Index hit a record in the first quarter, reported Davenport-based RSM US LLP and the U.S. Chamber of Commerce. Business leaders were bullish on economic strength, the tax cuts, the labor market and increased spending, sending both the current index and the outlook to new records. The composite index was 136.7, a 4.5-point jump from the previous quarter. A reading above 100 indicates growth.