Cochrane’s Writing Tips

A condensed summary of John Cochrane’s Writing Tips for Ph.D. Students (2005). The advice is his and the wording here is a paraphrase, so read the original for his examples.

Organization

  • Find the one central, new contribution of your paper and write it down in a single concrete paragraph: state the result itself, not that you found interesting results.
  • Readers skim. Put the main result first and fill in detail afterwards, as a newspaper does, instead of building to a punchline in the last table.
  • Leave out the story of how you got there and the things that did not work.

Abstract and introduction

  • Keep the abstract to 100–150 words. Say concretely what you find, and leave other literature out of it.
  • Open the introduction with your contribution, not with philosophy, the literature, or policy motivation.
  • Give the fact behind each claim, such as the regression and the number, not just the conclusion it supports.
  • About three pages is enough for an introduction. A roadmap paragraph is optional.

Literature review

  • Explain your own paper before comparing it with others: readers cannot judge the difference until they understand your contribution.
  • Keep the review short and set apart. Focus on the two or three closest papers and on giving credit where it is due.
  • Be generous. Your paper does not need everyone else to be wrong in order to be interesting.

Body of the paper

  • Nothing should come before the main result unless the reader needs it to understand that result.
  • In an empirical paper, include only the theory the empirics need, and write down the specific model you take to the data rather than a general one.
  • Lead with the main result, follow it with the graphs and tables that show why it holds, then a limited set of robustness checks.
  • Keep the conclusion short: no full restatement, no research agenda, no speculation.
  • Move extra robustness checks, extensions and the general model to an appendix, online if need be.

Writing

  • Keep it short. Every sentence should earn its place, and a finished paper should rarely need more than about 40 pages.
  • Say each thing once. Phrases like “in other words” usually signal a repeat.
  • At every level, first say what you do, then why, then how it compares with the alternatives.
  • Frequent pointers forward and back, such as “as we will see” or “recall that”, suggest the material is in the wrong order.
  • Document your work so that another student could reproduce every number from the paper and its appendix.
  • Simpler is better. Less math and simpler methods make a paper more convincing, not less impressive.
  • Keep track of what the reader already knows. Most students assume far too much.

Footnotes, tables and figures

  • An aside that matters belongs in the main text, and one that does not should go. Footnotes are for material most readers can safely skip.
  • Give every table and figure a caption a skimming reader can understand on its own. For a regression, include the equation and the dependent variable.
  • Discuss every number you show. If it is not worth a sentence, drop it from the table.
  • Report two or three significant digits, in units that give readable numbers.
  • Label axes, define every symbol in the caption, and choose line styles that still show up when printed.

Style

  • Use the active voice and take responsibility for your claims. “I” is fine on a sole-authored paper.
  • Prefer the present tense, and keep tenses consistent within a paragraph.
  • Write plain subject–verb–object sentences with few clauses, short words and little jargon.
  • Do not praise your own results with adjectives; let readers judge them.
  • Cut empty openers such as “it should be noted that” and just make the point.
  • Follow “this” with a noun, so the reader knows what it refers to.
  • Give Greek letters names as well as definitions, and remind readers what they stand for.
  • Describe a model’s structure directly; keep “assume” for claims about the real world.
  • Spell out authors’ names, skip the opening quotation, and use italics sparingly.

Empirical work

  • Identification comes first. Explain what moves your right-hand-side variable, what makes up the error term, and why the two are unrelated.
  • Explain why your instruments move the regressor but not the error, and know when a variable belongs as an instrument rather than a control.
  • For every estimate, say which variation in the data drives it, for example within firms over time or across firms.
  • Ask whose behavior you are modeling, so you do not mistake a supply curve for a demand curve, and rule out reverse causality.
  • Use few controls. Do not control for the channels through which your variable works, and be suspicious of a very high R².
  • Show the stylized facts behind your estimates, not just test statistics.
  • Report economic magnitudes as well as statistical significance, and a standard error for every important number.

Seminars

  • Skip the motivation, literature review and preview of results; start with the main result.
  • Put equations, tables and graphs on slides rather than your script, and leave each slide up long enough to absorb.
  • Listen to the whole question and pause before answering. Keep paper at hand to note what to change.
  • Err toward simplicity: audiences absorb far less in one sitting than presenters expect. Speak slowly and clearly, and finishing early is fine.

Why it matters

  • Economics papers are essays, and good economists spend much of each project on the writing. Cochrane points to Zinsser’s On Writing Well and McCloskey’s Rhetoric of Economics for more.