Complex sentence: The Pew Economic Mobility Project's research shows that only forty percent of children in the lowest income quintile remain there as adults, and 70 percent remain below the middle quintile, meaning 30% moved up two quintiles or more in one generation.
Split into simpler sentences: The Pew Economic Mobility Project's research shows that only forty percent of children in the lowest income quintile remain there as adults, and 70 percent remain below the middle quintile. That means that 30% moved up two quintiles or more in one generation.