During the nineteenth century, occupational information about women that was provided by the United States census-a population count conducted each decade-became more detailed and precise in response to social changes. Through 1840, simple enumeration by household mirrored a home-based agricultural economy and hierarchical social order: the head of the household (presumed male or absent) was specified by name, whereas other household members were only indicated by the total number of persons counted in various categories, including occupational categories. Like farms, most enterprises were family-run, so that the census measured economic activity as an attribute of the entire household, rather than of individuals.
The 1850 census, partly responding to antislavery and women's rights movements, initiated the collection of specific information about each individual in a household. Not until 1870 was occupational information analyzed by gender: the census superintendent reported 1.8 million women employed outside the home in "gainful and reputable occupations." In addition, he arbitrarily attributed to each family one woman "keeping house." Overlap between the two groups was not calculated until 1890, when the rapid entry of women into the paid labor force and social issues arising from industrialization were causing women's advocates and women statisticians to press for more thorough and accurate accounting of women's occupations and wages.
The primary purpose of the passage is to
explain and critique the methods used by early statisticians
compare and contrast a historical situation with a current-day one
describe and explain a historical change
discuss historical opposition to an established institution
trace the origin of a contemporary controversy
C选项：Correct。描述和解释一个历史上的变化。文章第一句就提到了，什么什么是为了应对或回应“social change” 这必然是一个历史性的“change”。作者写这篇文章的主要意思即是要展示和描述这个逐步完善的职业信息的过程。此作者不带有明显的个人意见，而是以描述为主。