The increase in employment away from Central Business Districts raises questions about the continued applicability of the monocentric model and its prediction of the negative decline of density, yet the model continues to be used and produces reasonable results. This paper argues that while the development of multiple employment subcenters produces variation in density patterns resulting in declining goodness-of-fit of the negative exponential model when estimated using data for small areas, the overall pattern continues to be a general decline of density with distance. The negative exponential model is estimated using data on densities both for census tracts and concentric rings around the center for 43 large urban areas in the United States from 1950 to 2010. The R2 values for the estimates using the tract data decline steadily after 1970, while the ring estimates show only small decreases. It is further hypothesized that since more general measures of accessibility to employment may now better predict density at the tract level, distance to the center as a proxy incorporates increasing error, resulting in attenuation bias in the estimates of the density gradients, which was shown by comparing the tract and ring estimates.