Saturday, January 7, 2017

Jagger's Theorem

Recently I watched (for the n'th time!) The Big Chill. If you're a fan of this movie, and its terrific sound-track, then this post will be even more meaningful to you.😊

And if you're reading this because you thought it might be about Mick Jagger, then you won't be disappointed!

Before we go any further, let me make it totally clear that I stole this post's title - I couldn't have made up anything that enticing no matter how hard I tried!

With that confession, let me state Jagger's Theorem, and then I'll explain what this is all about.

Jagger's Theorem:  "You can't always get what you want."
The latest issue of Amstat News includes a piece written by Arthur Kenickell, a member of the Board of Governors of the Federal Reserve System. It's title is, "Crooked Roads: IRS Statistics of Income at 100". (See p.25.)

I love the opening paragraph of Arthur's article - here it is:
"The most famous living economist, Mick Jagger (London School of Economics graduate*), has offered much wisdom, but perhaps the useful for those of us in statistics and related areas is what I call Jagger's Theorem and Corollary:
Theorem: 'You can't always get what you want.'
Corollary: 'But if you try sometimes you might find you get what you need.'
The proofs are left to the reader."
(*Actually, Jagger was an LSE student, but didn't graduate from that institution.)

This leads to one of the major themes that's developed in Arthur's article.

Arthur argues (correctly, in my view) that sometimes what we'd like to achieve with our statistical (or econometric) analysis simply can't be done. Either the necessary data can't be obtained, or the current methodology is too weak. Nonetheless, even in these circumstances we should persevere, and be creative. "In research, what we actually need very often comes clear only after a painful path of jettisoning wishes that we come to realize were unrealistic or unnecessary."

I think that's worth keeping in mind, and passing on to our students.

© 2017, David E. Giles


  1. But Mick Jagger never graduated from LSE.

    1. Sorry for perpetuating Arthur's error - I've added a comment in the post. Thanks!

  2. I recall reading that Mick Jagger’s favorite economist was Friedrich Hayek. But I can’t find a cite on that. Do you know?

    1. David - that's interesting! I don't have a reference - sorry!