Update: Thanks to Spike for pointing out that the Washington Post made a huge typo in their chart - the percentage of children under 5 who are Black and Asian was switched. Black children actually represent 15% of all children under five. Here's the correct chart.
The Washington Post has a story on a census report which discusses the race of children under the age of five. The census found that 45% of Americans under the age of five are members of a racial/ethnic minority compared to 33% of America's total population.
However, the chart at the bottom of the page shows that black children under five represent only 4% of the population younger than 5 even though African-Americans represent 13% of America's total population. While other minority gourps like Asians and Hispanics have a much higher percentage in the under 5 population, African-Americans have a much lower percentage.
Where are all the black children? They've been aborted. According to the Centers for Disease Control, 36.6% of U.S. abortions performed in 2002 were performed on Black women. This percentage has held fairly steady since the early 1990's.