Contemporary perspectives highlight significant inequality in early modern Spain. Quantitative measures of inequality are often either broad and rough or based on local or scattered estimates, which do not offer a precise overall picture over time. The sale of the Bull of the Crusade provides an opportunity to examine inequality trends consistently in early modern Spain. The Bull of the Crusade was a form of almsgiving granted by the Pope and collected by the Hispanic Monarchy, widely purchased by a population convinced of its spiritual benefits. There were two types of bulls: the standard 2 Reales bull for ordinary people and the 8 Reales bull for the wealthy and individuals of high social standing. We argue that the ratio of the 8 Reales to the 2 Reales bulls sold reflects concentration at the upper end of the distribution. Three main phases emerge: fluctuations around a flat trend from 1570-1630, a sustained decline in the following century, and a notable upward trend thereafter, reaching its peak in the late eighteenth century. A closer study reveals distinct patterns within the Crown of Castile and the Crown of Aragon that converged in the late eighteenth century.