Divorce Trends in R

I am working on "Divorce Trends" (using R studio to analyze data). While looking at the numbers I realize there a few factors I am confused/unsure about, especially on how the US Census measures the these trends, is it are they using refine or crude measures for calculation?

Also, how can I become a US Census "expert"? Any advise? I'm working on multiple trend researches but sometimes is difficult to find ID numbers from years previous to 2019, and finding some other topics.