Here. Take another look at yesterday's graph:
|Graph #1: Exponential Growth of Real Debt Across Four Periods, 1948-1993|
The black lines on #1 are exponential trend lines drawn by Excel for four different time periods. I used simple rules for selecting dates to figure the trend lines: Each period should be ten years or more in length, and aim for the maximum R-squared value.
After the thing posted on Monday morning I watched the graph for a while and started wondering what the growth rates are, the growth rates of the four exponential trend lines.
So in the Excel file I formatted the trendline label to make the numbers show 12 decimal places. Then I copied the exponents from the four different trendlines and pasted them together on a new sheet, along with the start- and end-dates Excel used to figure the trendlines.
Then I did my usual thing: I made a graph. I made a graph of the trend line growth rates.
The graph showed a straight line. I thought I messed something up. So I made it show a dot for each of the four data points. The dots all showed up on the straight line. So I know I didn't mess up.
It's a straight line. The increase in real debt growth is a straight-line increase, regular and consistent.
I recreated the graph as a vertical bar graph. It seemed right, as there are only four data points. And then I put the same data on the graph again as a line, like I had it the first time. With dots and all. I made the line black so it looks like a trend line. But it's not a trend line. It's a plot of growth rate data. And it's a straight line increase, regular and consistent:
|Graph #2: Exponential Growth Rates of Real Federal Debt|
// The Excel file