A significant factor pulling down first-quarter GDP, inventories for March showed contraction for wholesale inventories and a slowing build for retail. Wholesale inventories fell 0.4 percent on the month to reverse February's 0.4 percent gain, while inventories for retailers rose 0.3 percent which was down from February's 0.5 percent build.

Details for retailers show a 0.1 percent decline when excluding vehicles that followed a 0.3 percent build in February on this measure. Vehicle inventories rose 1.1 percent in March on top of February's 0.9 percent build.

Retail inventories measure the monthly dollar value of inventories held by retailers. The advance report is released late in the month for the following month and is part of the Monthly Advance Economic Indicators report (which also includes data on wholesale inventories and international trade in goods). Final monthly data for retail inventories are released about two weeks later with the Business Sales and Inventories report.

Investors need to monitor the economy closely because it usually dictates how various types of investments will perform. The stock market likes to see healthy economic growth because that translates to higher corporate profits. The bond market prefers a slower rate of growth that won't lead to inflationary pressures. Retail inventory data give investors a chance to look below the surface of the visible economy, especially for unwanted build. If inventories are growing too fast relative to economic growth, then both production and employment will probably have to slow while those inventories are worked down.