Since 1970, US milk production per cow has more than doubled resulting in large increases in feed intake. It is well established that increasing feed intake reduces diet digestibility. Our objective was to determine if the digestive efficiency of US dairy cows has also changed in the last 44 years. We assembled a data set consisting of diet digestibility measured via total collection or iNDF procedures with lactating dairy cows from studies published in the Journal of Dairy Science from 1970 to 2014. The data set contained 121 treatment means from 38 studies conducted at 16 US institutions. Based on regression analysis, milk yield and DMI increased by 20 kg/d and 8 kg/d between 1970 and 2014, respectively. Temporal effects on digestibility (DM, CP, or NDF) were determined using the regression model: Digestibility = YEAR₁₉₇₀ + CP + NDF; where YEAR₁₉₇₀ is the publication year minus 1970 and CP and NDF are diet constituents (% of diet DM) included to account for their effects on digestibility. DM digestibility decreased 0.13 percentage units per year (P < 0.01) for a total reduction of 5.7 percentage units since 1970. However, there were no temporal effects on CP and NDF digestibilities (P > 0.3). To account for the potential effect of feed intake on digestibility, DMI as a percentage of BW (DMI_BW) was included in the regression model. With DMI_BW in the model, DM digestibility decreased 0.08 percentage units per year (P = 0.03) for a total reduction of 3.5 percentage units. This suggests that only a portion (39%) of the decline in digestibility was due to level of feed intake. In contrast, CP digestibility was unchanged over time (P = 0.94), and NDF digestibility increased 0.14 percentage units per year (P = 0.05) when the model included DMI_BW. Increased NDF digestibility was likely due to the use of more highly digestible NDF sources in more recent studies. These results suggest that digestive efficiency has decreased by nearly 6 percentage units over the last 44 years. Perhaps genetic selection of cows for high milk production has inadvertently resulted in cows with high feed intake capacity irrespective of effects on digestive efficiency.