Questions about 1970 Census Data

If I am going to use 1970 census data for analysis, is that appropriate for me to use the combination of the first four datasets: 1970 1% Form 1 State, 1970 1% Form 2 State, 1970 Form 1 Metro, and 1970 Form 2 Metro to conduct analysis?

Technically, since these samples were drawn simultaneously (and therefore contain none of the same cases), you could combine all of the 1970 samples into one data file. However, each sample does contain a different set of variables and the geographic definitions vary across the samples. So, practically speaking, using them all together is not very well suited for most analyses. A list of the key details that differentiate these samples is available on the samples description page. Additionally, a fully detailed description of the 1970 samples can be found here.