Martin Luther King's Nightmare

Demonstrators wearing "I AM A MAN" signs protest outside LaGuardia Airport during a protest march in New York, January 15, 2015. Scores of airport workers gathered to rally on Thursday in New York and other cities to demand higher wages in one of several protests planned by an array of interest groups to mark the birthday of civil rights leader Martin Luther King, Jr. Mike Segar/Reuters

What would Martin Luther King Jr. think of America in 2015 if he'd lived to see his 86th birthday? No doubt he'd be pleased by the legal and political advances of black Americans, crowned by the election and re-election of President Obama.

But King would be disturbed by the stubborn race gaps that remain, especially in opportunity, tarnishing the idea of the American Dream. In terms of opportunity, there are still two Americas, divided by race. Five facts show how far we still have to go.

1. Half of Black Americans Born Poor Stay Poor

Upward mobility from the bottom of the income distribution is much less likely for black than white Americans: 51 percent of the black Americans born into the lowest fifth of the earnings distribution remain there at age 40:

2. Most Black Middle Class Kids Are Downwardly Mobile

Downward intergenerational social mobility from the middle to the bottom is much more common among black Americans. Seven out of 10 black Americans born into the middle quintile fall into one of the two quintiles below as adults. In some ways, this is an even more depressing fact than the poor rates of upward mobility. Even black Americans who make it to the middle class are likely to see their kids fall down the ladder:

3. Black Wealth Barely Exists

Race gaps in wealth – already wide – widened further during the Great Recession. The median wealth of white households is now 13 times greater than for black households – the largest gap in a quarter century, according to analysis by the Pew Research Center. Black median wealth almost halved during the recession, falling to $11,000 in 2013 from $19,200 in 2007:

4. Most Black Families Are Headed by Single Parent

Black children are much more likely to be raised in a single-parent household, and as our own research suggests, family structure can play a large role in a child's chance of success in all stages of life:

5. Black Students Attend Worse Schools

The school system remains highly segregated by race and economic status: Black students make up 16 percent of the public school population, but the average black student attends a school that's 50 percent black. Our colleague Jonathan Rothwell shows that the average black student also attends a school in the 37th percentile for test score results, whereas the average white student attends a school in the 60th percentile:

There are race gaps in almost every conceivable social and economic dimension, many of which we have discussed on these pages before: incarceration, early learning, parenting, schooling, attitudinal racism, employment -- the list goes on. There has been progress, too, of course. But one thing is clear. An inescapable requirement for building an opportunity society is improving the life chances of black Americans.

Richard V. Reeves is Senior Fellow, Economic Studies, and Policy Director, Center on Children and Families at the Brookings Institution. This article first appeared on the Brookings Institution website. Follow Richard V. Reeves on Twitter @RichardvReeves