Hypothesis: It takes 3 human generations of economic growth agnostic to a given cultural rift to heal said cultural rift. If there's a power gradient across the rift, you need more generations. Any flagging of growth reactivates the rift and resets the 3+ generation clock.
Seems too neat / linear. Look at Northern Ireland peace process for a counter-factual. Also, how do we define "healed". Absence of violence? Absence of hate speech? To what baseline level? Do we exclude 4Chan and Reddit as outliers?