Disclaimer. After nearly 40 years managing money for some of the largest life offices and investment managers in the world, I think I have something to offer. These days I'm retired, and I can't by law give you advice. While I do make mistakes, I try hard to do my analysis thoroughly, and to make sure my data are correct (old habits die hard!) Also, don't ask me why I called it "Volewica". It's too late, now.

BTW, clicking on most charts will produce the original-sized, i.e., bigger version.

Friday, May 4, 2018

Seasonal adjustment factors for World EV sales

I said in my last post about world EV sales that I suspected that something was awry with my seasonal adjustment program.  World EV sales appeared to dip sharply in January and February of this year, and I thought that was probably because the seasonal factors were wrong. 

I went back to the gospel (The manual for the X-11 FORTRAN program entitled THE X-11 VARIANT OF THE CENSUS METHOD II SEASONAL ADJUSTMENT PROGRAM), issued by the US Dept of Commerce back in 1967, written (I've just noticed) by Julius Shiskin, a remarkable econometrician.  I examined the weights/algorithms I had been using in my seasonal adjustment program, and realised that when I wrote it 30+ years ago, I used several short cuts to get it up and running quickly.  In the way these thing happen, I never got around to replacing the quick and dirty fixes I'd made with a more, shall we say, thorough working.

Anyway, this is what seasonally adjusted world EV/PHEV sales look like now (I haven't added the new data for March--I'll do that chart tomorrow.  It's late, for me, and I'm off to bed shortly).  As you can see, the values for January and February this year are somewhat higher than they were.

I just thought I'd let you know, as I said I would examine my program for flaws.  Which took longer than expected because I had to work out anew what I'd done the first time, and I kept on thinking WTF?  Anyway, all done.

À demain!

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