I really like
this price chart (that I found on the bottom of this page):
 |
Weekly U.S. Retail Gasoline Prices, Regular Grade
For the 18 months ending December 2009. |
It is clear and easy to read. (Or it would be if it was full size. Click on it to see the full size version.) However, it is a little deceptive: it looks like the price of gasoline went all the way to zero back just about a year ago. I will grant that after the sky high prices of summer before, it almost did feel like zero. But it wasn't. Gas was still $1.60 a gallon, six times as much as it was when I first started driving (my personal baseline). I understand the desire to make the data more dramatic by raising the baseline to emphasise the amount of recent change. Lots of people do it. Maybe it's something they teach in presentation school, but it is basically wrong. A chart like this should have a baseline of zero. If you want to also include a chart with special emphasis, like this one, that's fine, but don't leave out the true picture.
Here is a chart I made using a Google Doc's Spreadsheet. I got the data from another page on the same
EIA website that the first chart came from. This one has a baseline of zero, and goes all the way back to, whoa, 1993. Gee, a whole 16 years. The big drop in prices of a year ago still shows up as a big drop. Unfortunately, the dates on the X axis are all but unreadable.
 |
West Coast Gasoline Prices
1993 to 2009 |
H/T to
MaxedOutMama.
Update October 2016 replace missing graphs.
Charles,
ReplyDeleteas long as both axes are labelled and scaled, it's honest. In fact, suppressing empty parts of the graph 0<Y<1.60 helps improve the resolution on the visible part :-)
Pergy:
ReplyDeleteLast year this time, gasoline was actually trading at a NEGATIVE price. By that I mean, the gasoline price was actually trading below the value of the unrefined crude oil (in dollars per gallon.)
I bought the gasoline and shorted the crude oil and made over 12$ per barrel as "normalcy" returnsed during the spring of 2009. See:
http://onehonestman.wordpress.com/2009/01/14/gasoline-crack-spreads-and-free-lunches/
This sort of condition is extremely rare -- but then again the end-of-the-world doesn't happen too frequently either. ;)
Stu - I didn't say it wasn't honest. I said it was deceptive. Far too often I see charts that look like this and the hyperbole surrounding them makes it sound like the bottom has completely fallen out when in fact the price has droped a fraction of a percent because the X axis would be 500 feet down, and that is only if they have labeled the Y axis, which they oftentimes forget to do. Yes, a true zero would cost you some white space but it would give a better picture of the overall situation. Specialized graphs which exaggerated views of activity are for specialists who live and breath this stuff. They are not for the generally public, i.e. I don't like them and will protest whenever I see one.
ReplyDeleteRocky - How were your nerves when you made this purchase? It sounds like a sure thing, but was it really? Could things have gone South?
ReplyDelete