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Writing an Empirical Paper

Writing an Empirical Paper. Andre R. Neveu 9/10/2008. Empirical vs. Theory. “Capstone” Bring theory to data Does theory pass the test? Ex: Immigration causes wages to fall Rewarding and frustrating Learn through struggling You get to be “creative” Useful in interviews.

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Writing an Empirical Paper

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  1. Writing an Empirical Paper Andre R. Neveu 9/10/2008

  2. Empirical vs. Theory • “Capstone” • Bring theory to data • Does theory pass the test? • Ex: Immigration causes wages to fall • Rewarding and frustrating • Learn through struggling • You get to be “creative” • Useful in interviews

  3. Art is long, and time is fleeting, -Longfellow • Decisions • Research question • Motivation and background • Literature Review • Empirical Strategy • Theory • Data • Methodology • Write-up

  4. Choosing a research question • Examine what brought you to economics or captivates you right now • Favorite textbook (see callouts and footnotes) • Pop-econ • Blogs • Scan journals (JSTOR/Google Scholar/EconLit) • Replication/Extension/New Data

  5. Motivation and Background • Once you have your topic • Find competing viewpoints • Often found in other papers’ literature reviews • Note data used by authors • Note criticism! • How have others approached the topic • Data types & novel data • Regression method • Competing theory • Make sure your topic is “approved”

  6. Literature Review & Theory • Read many abstracts and introductions • Does paper really study your idea? • Ex: Great Moderation models and “Learning and the Great Moderation” (Bullard and Singh 2008) • Sometimes papers study different theories and ideas completely, but it is very relevant to your method (Ex. “Minimum Wages and Employment: A Case Study of the Fast-Food Industry in New Jersey and Pennsylvania ” Card and Krueger 1994)

  7. Empirical Strategy • Theory • Data • Methodology

  8. Theoretical Foundation • Solid theoretical foundation or framework • Testing a previously developed and often previously tested theory • “Tweaking” or “combining” theories • Stretch assumptions • Unless you have examined one theory before, avoid comparing different theories

  9. Data Types • Tools and Methods differ • Cross-sectional • Panel • Time Series • Limited Dependent Variables

  10. Cross-sectional Data • See Studenmund or Wooldridge intro books • Heteroskedasticity • Non-linearities • Multicollinearity • Instrumental Variables • Simultaneous Equations

  11. Panel & Pseudo-panel Data • See Wooldridge Econometric Analysis of Cross Section and Panel Data • Two or three years? • Difference-in-difference (DD) or difference-in-difference-in-difference (DDD) • Multiple years • Fixed Effects • Random Effects

  12. Time Series • See Walter Enders Applied Econometric Time Series • Heteroskedasticity • Unit Root/Stationarity • Vector Autoregression (VAR) (c-i-y) • Granger Causality

  13. Limited Dependent Variable • Probit and Logit Models • Probability (01) • Ordered Models • Ex. Number of doctor visits/arrests • Multinomial Models • Ex. Types of contraception • Truncation and Censoring • Wages of non-workers? Topcoding?

  14. You are facing a time constraint • Can you obtain the data you need? • How narrow is your topic? • Do you know how to use the software to analyze your idea?

  15. Where can you get data? • dataferrett.census.gov • American Community Survey (ACS)American Housing Survey (AHS)Behavioral Risk Factor Surveillance System (BRFSS)Consumer Expenditure Survey (CES)County Business Patterns (CBP)Current Population Survey (CPS)Decennial Census of Population and Housing (Census2000)Decennial Census of Population and Housing (Census1990)Delaware StatisticsHarvard MIT Data Center Collection Home Mortgage Disclosure Act (HMDA)Maryland Statistics National Ambulatory Medical Care Survey (NAMCS)National Health and Nutrition Examination Survey (NHANES)National Health Interview Survey (NHIS)National Survey of Fishing, Hunting, and Wildlife-Associated Recreation (FHWAR)Small Area Income and Poverty Estimates (SAIPE)Social Security AdministrationSurvey of Income and Program Participation (SIPP)Survey of Program Dynamics (SPD)

  16. Where can you get data? • Bureau of Economic Analysis • Bureau of Labor Statistics • Resources for Economists • http://www.rfe.org/showCat.php?cat_id=2 • www.freelunch.com

  17. Now what do you do with it? • Try to put your data directly into SPSS (or your preferred software) • You MUST have a “codebook” for your own purposes • Gender = 1 or 2? • Race = 1, 2, 3, 4, or 5? • CLEAN your data so you can read it AND work with it • Missing values? • Zero hours of work?

  18. Software GUI • SPSS is available campus-wide (Norusis books) • EViews has affordable student options Coding • Mathematica is available campus-wide • SAS may be available • Matlab if you are ambitious (affordable student option) • R is free (open-source and spreading) • Other options are expensive and not “locally” supported

  19. Theory should guide your data • Many datasets have hundreds or thousands of variables • KNOW what you want before you dig for data • Use literature review to guide you to the right datasets • Don’t find the best regression and then justify it with theory

  20. Setup your Null and Alternatives • You should decide what you are testing before you begin • Significant novel results are hard to obtain • “If it was so easy…” • Statistical versus practical significance • Direction and magnitude

  21. Do Your Empirical Work • Run your simplest regression model • Add variables to your simple model • Make adjustments to your model • Instrumental Variables, Fixed Effects, etc… • How do you confirm statistical significance? • Do you have problems with inference? • Are individual estimators significant? • Are overall models significant? • Avoid “digging” or “mining”

  22. You should NOT include an SPSS printout. Carefully organize your data and tests for inference

  23. Excerpted from Card and Krueger (1994), Minimum Wages and Employment: A Case Study of the Fast-Food Industry in New Jersey and Pennsylvania.

  24. Now you can write Suggestions • Motivation and research “statement” • Write literature review FIRST • Helps to guide development of your theory section and frame your position • Describe data • Empirical analysis • Conclusion • Introduction & Abstract • References • Title • Proofread

  25. General guidelines • Newspaper or “triangular” style • Brief • Try to get your point across in fewer words • Cite everything • Assume your reader is familiar with regression analysis • Use footnotes to keep text flowing or present tangential topics

  26. Literature Review DO • Note the most important contribution of all references • Include more than three references • Include all VERY relevant literature • Refer to methodological papers • Cite any ideas that are not yours DO NOT • Include every paper you looked at • Reference your textbook to describe OLS • Cite Wikipedia • Give extensive recaps of previous work

  27. Theoretical Section • Justify your empirical work • If theory is limited, try to explain in words • Show your functional form DO NOT • Rehash all competing theories • Write out:

  28. Data • Provide sources on all variables • Provide summary statistics on all variables in well-organized table (usually mean, SD, and range are sufficient) • Include units • Read “decimal places” section • Make data and analysis available for others DO NOT • Rewrite your data dictionary • Split tables over several pages • Report hundreds of pages of output • Include straight SPSS or Excel output

  29. Empirical Section • Not a data summary • Compare your results to the previous literature • Not the time to introduce a new article • Be specific about previous literature’s findings • If nothing is significant, what about direction

  30. Conclusion • Restate the research question • Provide your answer • Restate most important results in relation to previous literature • Best areas for further research

  31. Introduction & Abstract • State the research question • Motivation (short) • Results • Do your results conflict or support previous literature? • Abstract should really only contain your research question and results

  32. References and Footnotes • Choose a standard style (I prefer Chicago) • Include everything you reference in your paper • Don’t add references you don’t use • Avoid citing textbooks (unless relevant) • Use footnotes to keep text flowing, for references, and brief discussions.

  33. Abstract: 100-150 Words State your findings Introduction: Restate your findings! Motivate your research Not a literature review but can mention some previous work

  34. Presenting your work • Similar fashion to your final paper • Tell the punchline first • You are facing a time constraint • Clarity and brevity • Diagrams are often work, but helpful

  35. Not a table for the middle of your paper. If you MUST include a table like this, you should add it in an appendix!

  36. A table that is difficult to understand in your paper… is even worse in a presentation!

  37. Peer Review • Get your paper done early • Give your paper to friends, teachers, or the writing center to proofread your paper • Accept criticism, improve your paper, and move on • Wait 24 hours • Reread your paper and revise it

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