I would think that urbanization would have been very high in the 70s and 80s as all the rural born baby boomers graduated high school and moved to "The Cities". But the boomers also tended to move to areas that may have been considered rural during that time, but with rapid growth, were then reclassified as urban areas in the 1990s.
That's so weird, the opposite could be said in New Jersey. All the city-born boomers were moving away, especially in the '70s and '80s.
Flight from the cities occurred here during the 1950s and 60s. By the 70s, the population fell at the fastest rate as the white baby boomers that grew up in the city moved out. Unlike in some cities (like Detroit, Cleveland, or St. Louis), the Twin Cities has had constant growth in the number of households in the cities since they were incorporated. It's simply the huge decline in household size that has led to population decline.. again indicating that the flight wasn't as big among long time adult residents.. but the simple lack of room for the kids to stay in the city when they moved out.
That's also why some suburbs had a spectacular boom followed by a huge decline in population and then stabilization. Richfield grew from nothing in WWII to 47,000 residents in 1970.. and fell to 36,000 in 1980 and 33,000 in 1990... that extra 11,000 people were all kids who graduated and moved out of the city in the 1970s.
It's such an incredibly inefficient way to use infrastructure.. but people wanted their 0.5 acre/2.5 kids and a white picket fence on a quiet street.
