His data series are GPSAVE and GPDI. I know that for a fact.

I happened upon a post from Paul Krugman from 2011. In it he says "Here’s gross private saving minus gross private investment — the private-sector financial surplus" and he shows this graph:

Graph #1: Krugman's Graph

The graph is from before both the 2016 revision and the 2014 revision to the FREDGraph system.

I know from Krugman's brief description what he is showing. And I know from from the graph itself -- from the top border -- which data series he used to make the graph. I also know (from the left border) the units for each series. So I can duplicate the graph easily:

Graph #2: Duplicating Krugman's Graph

I started my graph in 2001 like Krugman did, but didn't stop it with the 2011 data. Mine shows extra years. Also, my high point is around 1400 billion while Krugman's is less than 1200 billion. So I know there was a data revision some time between 2011 and today.

But here's the point. Suppose you wanted to duplicate my graph. Could you do it with confidence?

When I look up Gross Private Saving at FRED I get a list of 102 data series. They're not all named Gross Private Saving, but two of them are.

And when I look up Gross Private Domestic Investment FRED gives me a list of 1103 series. Turns out only two of them are named Gross Private Domestic Investment. So we are lucky this time. There are only four possible graphs we can make at FRED where the title will say Gross Private Saving minus Gross Private Domestic Investment. Given the number of options FRED gave me, it could have been more than a hundred thousand.

In 2011, there was no such ambiguity in FRED graphs.

When I started using FRED graphs, their greatest feature was their trustworthiness. You could identify the data precisely. You could identify the data units precisely. And that information came directly from FRED. You could duplicate somebody else's graph and then look at different years, or all the years. You could tweak it and try different things. But you were sure of your starting point: You knew the data and you knew the units.

That's no longer true. And that's a shame.