The actual table I used from the Census was Educational Attainment--People 25 Years Old and Over, by Total Money Earnings in 2010, Work Experience in 2010, Age, Race, Hispanic Origin, and Sex
but I just pulled out the total number for the entire population.
I picked the data for people over 25 years old. So there are various folks under the age of 25 who are not included. If you want the information including people 18 to 24 years old then that is also available. I figured that looking at people age 25 years and older would be a little more meaningful. There are a lot of folks 18-24 who are still settling into their occupations or working a transitional job after college, etc.
First here is how the income distribution looks per income $5,000 group :
Now heres a pie chart just showing large $25,000 chunks of income :
As you can see there is also a large % of the population that makes no income. These would be people who do not work for various reasons.
Now lets look at how the income groups are if we exclude the people who have no income :
This is what I think is the real meat: Among the population over age 25 with earnings, about 1/3 of people make under $25,000, another 1/3 make between $25,000 and $50,000 and the other 1/3 make over $50,000.