Answer:
Crime rates increased because the necessary conditions for it appeared during these decades: a likely offender, a suitable target, and lack of guardianship.
Explanation:
Lawrence Cohen and Marcus Felson developed a theory of crime opportunity called "routine activity theory". According to this theory, crime is not necessarily a byproduct of social issues like poverty or unemployment. The researchers noted that crime increased the most during the post-war economic boom (between 1960 and 1980), which runs counter to the popular notion that poverty and inequality are the main causes of criminal behavior.
Instead, Cohen and Felson argue that when the elements that enable crime all appear at the same place and time, it is more likely to occur. These conditions are: a likely offender, a suitable target, and lack of guardianship. The economic prosperity of the post-war years set the foundations for the soaring crime rates: criminals had more tools at their disposition to commit crimes, like access to guns and getaway vehicles; changes in lifestyle led to more people (including women) entering into the workforce and leading riskier lives, while increased material prosperity made them more inviting targets; and finally, the absence of enough deterrents (such as guardianship provided by an object or another person).
