This research discloses the classification criteria used to define the population with disability in the twentieth century census records in Costa Rica and therefore gives an approximation of the conceptual formulations needed to refer to the examined group. Additionally, a segment of the population has been characterized by sex, age, marital status and geographical distribution. Other aspects like literacy rate, education level, occupation, head of household and housing were also dealt with. The disability concept based on deficiency, which defined the classification criteria for the population in those data sources, is among the most significant findings of this research. Furthermore, it was found not only a relation between disability and inequity during that century, but also the fragility of family ties in that population group as compared to the rest of Costa Rican households at the end of the century. Data sources used for this research were the population censuses in Costa Rica during the twentieth century. Data processing was primarily based on the descriptive analysis of frequency distribution tables.

Keywords: Disability, census, classification, conceptual development, socio-demographic characteristics