Source: US. Bureau of the Census
The U.S. Census Bureau maintained time series of monthly sales and end-of-month inventory estimates of retailers based on the Standard Industrial Classification (SIC) system. The SIC-based time series were discontinued as the North American Industry Classification System (NAICS) time series were newly introduced.
US. Bureau of the Census, Retail Sales (DISCONTINUED) [RETAILNS], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/RETAILNS, July 26, 2016.