The lack of equal opportunity and upward mobility when there are high levels of economic inequality is most dramatically clear when looking at children. Children born and raised in low income families are more likely to have:
- health problems at birth,
- worse living conditions including toxins in their environment (e.g., lead and air pollution),
- worse nutrition, and
- less nurturing and stimulating care from parents and non-parental caregivers.
Therefore, the opportunity for children in low income households to achieve their full potential – the foundation of equal opportunity and mobility – is compromised literally from day one. Growing up in an environment that is likely at times to be unhealthy and stressful can do long-term harm to a young child’s developing brain and, therefore, to his or her chances for success in school and in life. 
The relationship between a child’s family’s income during childhood and his or her life outcomes is well-established. Decades of research have established that a child’s family’s socioeconomic status is the strongest predictor of a child’s success in school and in life.
Without a very robust safety net and system of supports for low income families – which conservatives oppose both philosophically and fiscally – high levels of income and wealth inequality leave lower income children behind from birth (and probably even pre-natally).
Children from families with lower incomes and wealth also receive much less financial support from parents, both during parents’ lifetimes and through inheritance. Many parents who have the means provide financial assistance to their children to further their education, to buy a home or a car, to start a business, or to weather a health or job-related setback. The ability to support children’s opportunities and upward mobility is inherently lower for families with less income and wealth than it is for well-off families.
The lack of opportunity and upward social mobility for those with middle class and lower incomes, not to mention those in poverty, is not a separate problem from the inequality of income and wealth, but part and parcel of it. For example, children who graduate from college but are from the 20% of families with the lowest incomes are two and a half times less likely to be in the top 20% of income earners as adults than children from wealthy families who did not even graduate from college. 
If we and our democracy are committed to equal opportunity and social mobility, we must address economic inequality. Public policies created the Great Prosperity of the post-World War II economy. Back then everyone shared in the benefits of economic growth, and income and wealth gaps shrank. The public policies of the last 40 years have undermined the middle class and fostered the growing economic inequality that now rivals that of any point in American history. Changes in public policies can reverse our economic inequality and restore the equal opportunity and social mobility that are cornerstones of our American democracy. 
 Pollak, S., et al. (July 2015). “Association of child poverty, brain development, and academic achievement,” JAMA Pediatrics
 Bernstein, J., & Spielberg, B. (6/5/15). “Inequality matters,” The Atlantic
 Reich, R. (2010). “Aftershock: The next economy and America’s future,” Random House books.