Occupation, 2010 basis consistency for groups

I am attempting to look at the history of all occupations that fall under “protective services” going back to 1950 using the OCC2010 variable. It is not clear to me whether this is consistent over time. It is easy to tell whether specific occupations go back to 1950 (some don’t), but I can’t tell if it works as a category.

It looks like the “protective services” category does go back and is roughly comparable over time. As is discussed on the OCC2010 variable description page: The Census Bureau has reorganized its occupational classification system in almost every census administered since 1850. All original occupational information is stored in the OCC variable. The meaning of codes in the OCC variable changes with each census year. The 2010 occupation coding scheme for OCC has 493 categories. In the interest of harmonization, however, the scheme has been modified to achieve the most consistent categories across time. That is, some categories that provide more detail in the 2010 scheme were grouped together because earlier categories are inseparable when more than one occupation is coded together. Specifically, “Protective Service” occupation codes all fall into the following range of codes: 3700-3950.