What does the "$-1" value mean?

One of the most often asked questions that we get is what does the $-1 mean. 

The "$-1" are what's known as jam values and are used when data are not available. There may be disclosure restrictions, or the sample size could be too small. Instead of leaving the field blank or using a text value, the "-1" is used so that you can sort the data but still know that there are no data available for this particular estimate. 

Jam Values for Medians

The following is a listing of the jam values for medians. For example, if there is an estimate of "2499" for table B10010, then it does not indicate a dollar amount. It means that the median is somewhere below 2,500 and thus is not calculated.

Source: US Census