Census information on general health and disability is used to smooth the health state prevalence seen in Annual Population Survey (APS) data. Previously, we used 2011 Census data for those purposes in estimating health state life expectancies between 2011 to 2013 and 2018 to 2020. With Census 2021 data available, we improve the accuracy of intercensal prevalence used in imputing and fitting health state prevalence. We use linear interpolation between the health state prevalence seen at Census 2011 and at Census 2021 to create period-specific estimates of health state prevalence for the intervening years 2012 to 2020. Linear interpolation estimates the value of function between two known values; in this case, the prevalence seen at the 2011 Census and 2021 Census.