Notes on my Gordon's Way calcs

Yesterday I said

I want to use Robert Gordon's method of evaluating economic conditions... I'm not doing it by throwing away all the data where there is no identical unemployment rate in both time periods. The way I'm doing it is by putting linear trend lines on scatterplots, and compare the trends.

Proofreading that, looks like I should have said "comparing the trends." Also, I realized that since I'm not "doing it by throwing data away", I don't have to round the unemployment numbers to one decimal place.

Next time, no rounding.


As part of the process of creating my "Gordon" scatter plots, after I made subsets of the data for selected time periods, I sorted them. For each subset I sorted three columns (unemployment rate, RGDP growth rate, and date) on the unemployment column. The sort puts my X-axis values in sequence, lowest to highest, the way they would be if I was putting date values on that axis.

(I didn't need the "date" column for the graph. I needed it to improve my confidence in my work.)

What happens if I don't sort the data? I found out when I forgot to do the sort. It looked like a cluster or spiral or something. I knew right away when I saw it that I did something wrong, and I fixed it right away. I didn't stop to look at it. So I want to graph the unsorted data again -- and look at it this time:

Graph #1: Unemployment Rate (X-Axis) and RGDP Growth Rate (Y-Axis)

Not a spiral. Maybe a "scatter". If you follow along the blue line from dot to dot, you arrive at the dots in chronological order. Uh, the dots are in chronological order, not you.

But looking at it, I get the impression that the dots are grouped, with empty space between the groups. Look at the dot closest to the upper-left corner: There are no dots below it! Three dots off to the left, maybe five to the right, but there is a big space with no dots below that upper-left one.

And look at the two highest dots, the ones above the 15.0 level. Below each of them is a broad white strip with few scattered dots in it. A little off to the left, a little off to the right, the dots are more tightly packed together. Odd, isn't it?

Maybe that's "random": unexpected groupings separated by unexpected empty space.

Then I remembered that I rounded the values. I ran into that problem before, where the dots got packed into groups by the rounding. I did the graph over right away, using the original, unrounded data:

Graph #2

Looks almost the same.

... ?

Oh, of course: Rounded to one decimal place, I could have nine dots side-by-side between 4.0 and 5.0 on the X-axis, with the dots separated by gaps only about the size of a dot. The grouping isn't from the rounding.

Then you get these strange ideas, like maybe there is some relation between unemployment and growth which favors certain places on the graph over other places.

... Nah.

But you have to think about those things, you know? Because one of those ideas could lead to the light bulb that works.