Economics - General

Writing Tips for Ph.D. Students

John Cochrane gives writing tips for Ph.D. students.  One of the key insights it the following:

Many economists falsely think of themselves as scientists who just “write up” research. We are not; we are primarily writers. Economics and finance papers are essays. Most good economists spend at least 50% of the time they put into any project on writing. For me, it’s more like 80%.

Below are some other highlights from this paper.

  • “Figure out the one central and novel contribution of your paper.  Write this down in one paragraph.”
  • “A good paper is not a travelogue of your search process.”
  • “The main point of the literature review should be to set your paper off against the 2 or 3 closest current papers, and to give proper credit to people who deserve priority for things that might otherwise seem new in your paper.”
  • In the body of the paper, your task is to get to the central result as fast as possible.
  • “There should be nothing before the main result that a reader does not need to know in order to understand the main result.”
  • “…the theory must be the minimum required for the reader to understand the empirical results.”
  • “As you edit the paper ask yourself constantly, ‘can I make the same point in less space?’ and ‘Do I really have to say this?'”
  • “Follow the rule ‘first describe what you do, then explain it, compare it to alternatives, and compare it to others’ procedures’ at the micro level as well as the macro level. For example, in describing a data transformation, just start with, say, ‘I adjust income by the square root of household size’. Then tell us why adjusting is important, and then talk about different adjustment functions. Most writers do all this in the reverse order.”
  • “Simple is better.”
  • “Don’t use footnotes for parenthetical comments.”
  • “The caption of a regression table should have the regression equation and the name of the variables, especially the left hand variable.”
  • “Good figures really make a paper come alive, and they communicate patterns in the data
    much better than big tables of numbers.”
  • “Much bad writing comes down to trying to avoid responsibility for what you’re saying.”
  • “Clothe the naked ‘this.’ ‘This shows that markets really are irrational…’ This what?”

What are the three most important things for empirical work?  Identification, Identification, Identification. Cochrane also has a list of tips for explaining your empirical work.

  1. What economic mechanism causes dispersion in the right hand variables?
  2. What economic mechanism constitutes the error term?
  3. Explain why you think the error term is uncorrelated with the right hand variables in economic terms.
  4. Describe the source of variation in the data that drives your estimates, for every single number you present. For example, the underlying facts will be quite different as you add fixed effects. With firm fixed effects, the regression coefficient is driven by how the variation over time within each firm. Without firm fixed effects, the coefficient is (mostly) driven by variation across firms at a moment in time.
  5. Think of reverse causality stories.
  6. Consider carefully what controls should and should not be in the regression. Most papers have far too many right hand variables. You do not want to include all the “determinants” of y on the right hand side.
  • High R2 is usually bad — it means you ran left shoes = α+β right shoes +γprice.  Right shoes should not be a control!
  • Don’t run a regression like wage = a + b education + c industry + error. Of course, adding industry helps raise the R2, and industry is an important other determinant of wage (it was in the error term if you did #2). But the whole point of getting an education is to help people move to better industries, not to move from assistant burger-flipper to chief burger-flipper.

Cochrane, John H. “Writing Tips for Ph.D. Students.”