Per capita and inflation adjusted numbers don’t tell the whole and accurate story. The percentages, however, do. People really don’t care what the actual numbers are, just how much the changes have been. I respectfully disagree because just going for the shock value of "Look how much the debt has grown since the 1700's" will bring the counter-argument one second later of, "Of course it has grown by a huge percent. The population has grown by a huge percent.".
It costs far less money to run a country of 4 million (the U.S. in 1790) than it costs to run a country of 308 million (the U.S. in 2010).
When a population has tremendous growth over time, even if the per capita debt is kept constant with impeccable financial conservatism, the total debt chart would be a mirror image of the population growth chart:
A “Per Capita” comparison attempts to rationalize debt. There are baseline numbers such as defense. How much defense today in 2011 does it take to defend this nation from known enemies? That number would be the same regardless if we had 100 million or 200 million citizens.
The purpose of the chart is to show the increase each political party has caused during their period of control. Comparing actual dollars from one year to the next is fine enough as few periods exceeded but a few years. The chart also shows percentage increases which helps define the differences.
A full analysis would be needed to determine fault, to include categories of expenditures, political pressures, agreements made, etc, when all people want to know is when a Republican or a Democrat holds the presidency, Senate or House what happens to spending. Does it go up a lot, a little, or down any? What about the relationship between the President and Congress? What about the Senate versus the House? This chart gives meaning to those questions by providing the data for the answers.