Miscellaneous Food Links

  1. In North Carolina, barbecue is serious business. Also see this old post by Don Taylor.
  2. This condiment, which is sadly too little known outside of Quebec, nicely complements a number of cold-weather dishes, and it is not difficult to make.
  3. Mike Roberts on Angus Deaton and commodity prices.
  4. The Geography of Food,” a (virtual) special issue featuring articles from many different journals, with a nice intro by my Macalester colleague Bill Moseley.
  5. A systematic review of urban agriculture and food security impacts in low-income countries.
  6. Why was food so bad for so long in the US?

‘Metrics Monday: Multicollinearity

Suppose you have the following regression model:

(1)           Y = a + b1X1 + b2X2 + …+ bKXK + e.

You have N observations which you use to estimate the regression. If NK, you will not be able to estimate the vector of parameters b = (b1, b2, …, bK). That’s because you have fewer equations than you have unknowns in your system–recall from your middle-school algebra classes that you need at least as many equations as you have unknowns in order to solve for those unknowns. So in econometrics, Nmeans that you cannot “solve” for b (i.e., it is under-determined), N = means that your equation has a unique solution for b (i.e., it is exactly determined), and N > K means that your equation has several solutions for b (i.e., it is over-determined).

Multicollinearity is the problem that arises when N is too small relative to K, or what Arthur Goldberger called “micronumerosity,” referring to too small a number of observations relative to the number of parameters. The most extreme version of multicollinearity is NK, in which case you cannot estimate anything. Continue reading

How to Read Academic Articles and Books

A question from one of our PhD students:

Hi Marc,

I have a general question about reading references. How do you usually do reference reading? Do you take some notes in any software in your computer? How can you recall the main ideas of a specific paper after you have read a lot relevant papers?

Do you know or have you written any (blog) article about how to read academic references for graduate students?

At first, I had no idea how to answer that question, but then I remembered that a long time ago, Kim Yi Dionne wrote a post addressing just that.

That said, let me state the obvious: You can’t read academic books and articles like you read novels or magazine articles, and developing the right method for reading academic articles is key to becoming a more effective researcher. The way I went about it was pretty simple: I just read, read, and read some more until I developed some good habits, which I can summarize as follows: Continue reading