Regarding that recent update of the FREDGraph system

I was trying to duplicate the Real Interest Rate graph from page 12 of James Bullard's Modernizing Monetary Policy Rules.

Bullard describes the data:

One way to get a handle on this variable is to consider the nominal return on a one-year Treasury bill and subtract the trailing 12-month inflation rate.

And again on his graph:

1-Year Treasury Rate Minus Dallas Fed Trimmed Mean PCE Inflation Rate

He made it easy to find and format the data I needed.

I got FRED's graph of the Trimmed Mean PCE Inflation Rate, brought in the 1-Year Treasury Constant Maturity Rate, and subtracted the one from the other. I grabbed the Page short URL for the graph.

Then I looked at it:

https://fred.stlouisfed.org/graph/?g=lGmc

Above the graph, on the line with the "Download" button, the calculation is correctly described. But the title of the graph reads ; Not Seasonally Adjusted. I thought they fixed that! Guess not.

But I thought the plotted line looked right, the same as what I had before I grabbed the Page short URL. So I took the next step and downloaded the data as an Excel file. Here are the first few lines of that file:

Okay, there is the Trimmed Mean PCE Inflation Rate on Row 8. But where is the 1-Year Treasury Rate?

There is no hint in the file that subtraction was done. Now I have to wonder if the numbers I got are before or after subtraction. A quick look: After, I think. But I didn't doublecheck that yet, because I'm not done finding errors.

I clicked the "Edit Graph" button and discovered that "b-a" formula I entered had changed to just "a":

No subtraction. So there you have it.

//

I started over. I put three lines on a new graph:

1. Trimmed Mean PCE Inflation Rate,
2. 1-Year Treasury Constant Maturity Rate, and
3. 1-Year Treasury Constant Maturity Rate - Trimmed Mean PCE Inflation Rate

Here's the graph:

Here is a peek at the data:

A subtraction was done and downloaded.

And the formula:

So far, so good.

Next, I take the Page short URL. That's the only thing I did.

The link shows a graph that looks like this:

Wait! Where is my red line?

That graph again, showing that it does include three datasets:

(You can click the graph to see it bigger)

The red line is hidden beneath the green, because the green no longer shows the result of subtraction.

In addition, the description of the red line includes the words "Not Seasonally Adjusted". But the description of the green line includes the words "Seasonally Adjusted". Looks to me like adding the seasonal adjustment note was one of the changes made during the update. Looks to me like this is where the coding error lies. And it looks to me like they increment the index variable that returns the seasonal adjustment information, when they should be incrementing something else -- maybe the index into the list of lines on the graph. Just a guess, looking from the outside.

The downloaded data:

Lines 9 and 10 are identical. (And both say NOT seasonally adjusted. (Perhaps this is a second error in the code.))

Finally, the formula:

The formula line no longer shows subtraction. But it did before I clicked to get the Page short URL.

This is seriously weird, and weirdly serious.