Population(s) by State(s): Singular or Plural?

Suppose a table has many groups, each group of which has one certain number. Then, which of the following is grammatically correct as(?)/for(?) the table’s title?

• Certain Number by Group (US Census used population by state.)
• Certain Number by Groups (US Code used population by states.)
• Certain Numbers by Group (US BLS used unemployment rates by state.)
• Certain Numbers by Groups (Oklahoma used unemployment rates by states.)