Krugman's argument here needs one more point at the end:
In December, says the Bureau of Labor Statistics, a one-pound loaf cost an average of $1.386. How much of that was the cost of wheat? As best I can tell, a bushel of wheat produces about 63 pounds of bread; wheat has lately been selling at around $10 a bushel; so we’re talking maybe 16 cents of that loaf of bread, or less than 12 percent of the price, reflecting the cost of wheat.
What I get from this is that wholesale food prices have a surprisingly small impact on the price of food, let alone on overall consumer prices. Again, not zero. But it’s not at all peculiar to see large commodity price rises while overall inflation stays low.One could take the last paragraph to mean that because the price of wheat is such a small part of the price of bread it does not weigh heavily on food inflation. That is not exactly right because it does not imply that the correlation between a rise in the price of bread and a rise in the price of wheat is less than 1 (a lot less for wild price swings), which is what we want. (Take the price of bread = other + wheat - no correlation on RHS variables - and not something crazy.) For example, keeping "other" constant, if the correlation was one-to-one then a $0.05 rise in the cost of wheat per bread loaf would be equivalent to a 30% change in the commodity price. If bread was all we bought then that would translate to a 3.6% change in consumer prices (inflation), which is not incredibly large but is above the 2% Fed target. The argument is salvaged if the correlation between wheat and bread prices is not exactly one, and sometimes a lot less than one. Then the price of wheat can eat into the gross margins, wages, or the rest of the "other" - pun intended.
It was not wrong, but I thought it was a bit unclear. Moving beyond Krugman's blog I think there is one other noteworthy issue.
The graph at the top of this blog is broken down into income cohorts and shows the average percent that is spent on food and gas for each segment. As you can see it isn't even close to the majority of expenditures for most income groups. However, it unfortunately does hit the poor the hardest since they spend a lot more of their income on essentials.
Chris Aaron Gaun
@Chris_Gaun
chrisgaun@gmail.com


