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  • Correct margins commands for logistic panel regression with categorical and continuous variables

    Hello everyone,

    I am running a logistic panel regression to determine how the enactment of the Sarbanes Oxley Act and the share of independent board members impact the likelihood of a firm to commit fraud in a certain period.
    My variables are the following:

    lag1SH_INDEP = share of independent board members of a firm in % (between 0 and 1) in the previous period
    SOX = dummy variable coded 1 for the years after SOX was enacted and 0 for the years before
    FRAUD_P = dummy variable coded 1 if a firm committed fraud in a certain period and 0 if it did not

    My goal would be to be able to make statements along the lines of "An X% increase in the share of independent board members results in a Y% decrease of the probability of the company committing fraud in the subsequent period".

    I run the following regression and then calculate the margins using the - , eyex() - option which I thought would give me the change of fraud probability in % for a change of independent board members in % according to my understanding of this file: https://www.stata.com/manuals13/rmargins.pdf


    Code:
    . quietly xtlogit FRAUD_P   i.SOX c.lag1SH_INDEP
    
    . margins, eyex(lag1SH_INDEP)
    
    Average marginal effects                        Number    of    obs     =    23,390
    Model VCE    : OIM
    
    Expression   : Pr(FRAUD_P=1), predict(pr)
    ey/ex w.r.t. : lag1SH_INDEP
    
                
    Delta-method
    ey/ex   Std. Err.      z    P>z        [95% Conf.    Interval]
                
    lag1SH_INDEP   -.8350884   .2050966    -4.07   0.000        -1.23707    -.4331064
    However, as I interpret it, that would mean an 83.5% decrease of fraud probability for a 1% increase in independent board member share, which seems unrealistic to me.
    Would anyone happen to know which mistakes I made and which command would give me the desired value? It would also be great to know whether - margins, dydx(SOX) - would be the correct command to determine the change in fraud likelihood for the post-SOX period?

    I am grateful for any help on this issue. As I am new to this forum, please excuse any errors in formatting or wording my questions, I am glad for any advice on how to improve this as well.

    Thank you in advance and best regards,
    Mara


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