A long term (1989-2008) decreasing trend in black carbon and organic carbon surface concentrations is indicated by insitu measurements (IMPROVE) in the United States in winter months. The observed percent negative trend is higher in the western United States than the eastern region. This study examines how the observed trend relates to emission inventories of black carbon and organic carbon. Attention is paid to the contribution of emissions from the residential sector to the observed decreasing trend particularly over the western United States. A chemical transport model is used to relate the emission inventories to concentrations. A variety of bottom-up emission inventories are tested. Multiple linear regression was used to estimate the anthropogenic sources contributing to trends in BC and OC concentrations in winter months over US. The larger relative trend of carbonaceous aerosols in the west appears to be driven by the larger relative contribution of residential and transport sources to this region.