The D0-14/D ratio: A new paleodemographic index and equation for estimating total fertility rates

Objectives: The objectives of this study were to develop a new subadult–adult ratio for application to sites with good infant representation and to produce an equation to estimate the total fertility rate for a population based on the age-at-death ratio. A new approach is required as current methods exclude the 0–4 years age category due to presumed underenumeration of infants. While this is true for some skeletal samples, others experience good infant representation. Materials and Methods: Using age-at-death data and total fertility rates for 52 countries from the United Nations database for the year 1960, we examined the correlation between three age-at-death ratios and the fertility rate. We also utilized linear regression to determine an equation for calculating total fertility rate from the ratio. Results: We achieved a correlation of 0.848 between our D0-14/D Ratio and actual fertility rates. This correlation was significantly higher (p <.05) than the other ratios examined, including the d5-14/d20+ by Bocquet-Appel and Masset () and the ₁₅P₅ index by Bocquet-Appel (). Discussion: The exclusion of infants can result in inaccurate demographic measures, particularly where subadults aged over 5 years of age experience robust survivorship. In addition to providing a solution for sites with good infant representation, this study indicates that the 0–4 years of age category possesses great predictive power when compared to other age categories. The regression equation provides a total fertility rate which is comparable with data regardless of their temporal origin. This method will provide more accurate demographic measures for bioarcheological sites with good infant preservation.