For example, "In the past, ten out of every fifty people died from natural causes and twenty out of every fifty people died from violence.
"Run-on sentence" can refer to a mistake of people learning to compose written English where an ungrammatical sentence is formed (which can be corrected by splitting into two sentences). It can also refer to a sentence in written English that is grammatical, but could be more easily parsed by a reader (without compromising the intended meaning) if it were broken up into two.
Your example has a temporal adjunct that modifies both of two coordinated clauses. It seems fine to me. Not a run on in either sense. The question to ask yourself is whether it would sound better as two sentences, not whether it is "run-on." (Then if the two-sentence version sounds better, the one-sentence version is "run-on")