Complex sentence: In North America, over 50% of the population were farm families only a few decades ago; now, that figure is around 1-2% (citation needed), and about 80% of the population lives in cities.
Split into simpler sentences: In North America, only a few decades ago over 50% of the population were farm families. Now, that figure is around 1-2% (citation needed), and about 80% of the population lives in cities.