Why has crime gone up 2% in the last 70 years?

Crime rates are a rather complex issue. One important methodological issue is not cherry-picking two specific years at random, but looking at overall trends over a 100 year period. If one looks as such data, one sees a statistical trend. The period from roughly 1900-1930 averaged approximately 8 murders per 100,000 people. During the period from approximately 1935-1960, murders per 100,000 people dipped to an historic low of approximately 4.5, then rose back to historical averages during the period from 1965 to 1995 and then declined again to close to their historic lows.
One of the more well-supported explanations of this curve has to do with the age structure of the US population. Most crimes are committed by young men, with criminality peaking in the late teen years and then gradually declining, with people over 65 committing the fewest crimes. The historically low periods of crime reflect the Depression and World War II in which there was a decline in birth rates and then a large number of young men conscripted into the army, fighting abroad rather than committing crimes at home. The baby boom and "Pax Americana" meant a dramatic increase in the young male population in the US in the peak crime years of the 1990s. An aging population, with young men representing a smaller portion of the overall population, corresponds with a decline in crime rates in the 2000s.
https://www.democraticunderground.com/10021998000

https://www.infoplease.com/us/crime/homicide-rate-1950-2014