When you checked the boxes on your census form, you probably did not pay much attention to the form design. But it is something the Census Bureau researches and gives a lot of attention. Something as simple as using vertical instead of horizontal boxes can have a big impact on how you read the form and the data we gather.
If one person’s eye misreads the form and checks the wrong box, it may not change percentages of statistics very much. But if even 1 percent of a large population checks the wrong box on a question, it could lead to an inaccurate picture of a smaller population.