Wu H, et al. - Researchers retrieved annual time series data, spanning 243 years between 1749 and 1991 for Sweden at the national level, using multiple sources with the aim to determined if there is a negative correlation, as predicted in the Trivers–Willard hypothesis (TWH), between the intensity of maternal stress and sex ratio at birth (SRB). The correlation between maternal stress and SRB was determined during three periods (1749–1991, 1749–1861 and 1862–1991) via performing a series of ARIMA (autoregressive integrated moving average) models. Per findings, there appeared no statistically significant correlation of most measures of stress with SRB over a period spanning 243 years, providing no support for the TWH.