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  • Fixed and Random Effects with AR(1) and Robust Standard Errors

    Dear Statalist,

    I’m writing my bachelor thesis at the moment. I want to reproduce a paper about the Phillips Curve relationship in the forecasts of professional forecasters. But I don´t know which estimation method I should use. I already informed me a lot but didn´t find what I am looking for.

    Unfortunately, I haven´t the do-File and I didn´t get response to my emails send to the author. So I decided to ask here for advice.

    My data are panel data and have long-format with N>T and are unbalanced. I include a year dummy for every single year to control for time fixed-effects.
    In the paper there is written: “we applied the fixed-effect estimator when the Hausman test rejects the null hypothesis, otherwise the random effect estimator was applied”. On plus cause of overlapping forecast horizons we have serial correlation in the error term by construction. To overcome this the author uses the serial correlation model AR(1) to account for the autocorrelation in the error term. Additionally, cause of heteroskedasticity we have to use robust standard errors.
    So I am looking for an estimation method which I can apply for random and fixed effects and where I can also include AR(1) and use robust standard errors to control for heteroskedasticity.
    Anyone konws a method like this? Or can I estimate fist without Robust Standard Errors and include them afterwards - is there a possibility?

    Here is a short summary, what I have already tried:
    • Xtgls: no option cause of N>T
    • Xtreg: don´t allows for ar(1)
    • Xtregar: don´t allows for robust standard errors
    • ...

    This is my first post in this forum, so don´t hesitate to let me know if there is missing some information for a proper answer.
    Best regards and thanks in advance!

    Hannah

  • #2
    Welcome to the forum. You'll get a a better response if you follow the FAQ on asking questions. Folks may not be that excited about helping you duplicate someone else's results.

    The first question is whether you're getting the right sample size and parameters on the coefficients. Some things change standard errors without changing the parameters. There are a ton of options in xtgls and related models that may be what you want.

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    • #3
      Thanks Phil!
      Actually I found out, that my sample size is diffrent from the one of the authors. So now I have to find a new method.

      Thanks again for your hint

      Hannah

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