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  • Dynamic Panel Data Model with fixed effects giving very different results.

    I have panel data over 58 periods and across the 50 US states which gives 2900 observations. I examine the effect of COVID-19 mandates on the proportion of people reporting mental health in a state. My model includes fixed effects and also lags of 3 COVID-19 mandates: Mask Stay and School.
    When doing a moving average over the lags for 4 periods before the period ( = 2 months since each period is 2 weeks) I get significant results.
    When using 4 lags of the dependant variable I get similar results that are also significant.
    However, when doing lags of the independent variables ( Mask, School, Stay ) for 3 periods I get very statistically insignificant values. I have my code below. If anyone can help me i would really appreciate it and please tell me if you need more info and how I can share it.

    1st regression:

    egen mask_time = mean(past_mask), by(Time)

    egen stay_time = mean(past_stay), by(Time)

    egen school_time = mean(past_school), by(Time)

    egen travel_time = mean(past_travel), by(Time)

    egen business_time = mean(past_business), by(Time)



    *Including controlls for time (moving average)

    reg mental_health emp deaths infections repub i.Time i.States business travel School Stay Mask mask_time stay_time school_time travel_time business_time if Time>=5
    estimates store US

    . reg mental_health emp deaths infections repub i.Time i. States business travel School Stay Mask mask_time stay_time school_time travel_time business_time if repub == 0 & Time>=5
    . estimates store DEM

    reg mental_health emp deaths infections repub i.Time i.States business travel School Stay Mask mask_time stay_time school_time travel_time business_time if repub==1 & Time>=5
    . estimates store REP

    coefplot US DEM REP, keep(Mask Stay School) xline(0) recast(bar) ciopts(recast(rcap)) citop barwidt(0.1) levels( 95 90)


    2nd:

    gen mental_health_L1 = mental_health[_n-1]

    . gen mental_health_L2 = mental_health[_n-2]

    . gen mental_health_L3 = mental_health[_n-3]

    . gen mental_health_L4 = mental_health[_n-4]


    reg mental_health School Stay Mask business travel emp infections deaths repub i. Time i.States mental_health_L1 mental_health_L2 mental_health_L3 mental_health_L4
    estimates store US

    reg mental_health School Stay Mask business travel emp infections deaths repub i.Time i.States mental_health_L1 mental_health_L2 mental_health_L3 mental_health_L4 if repub ==1
    estimates store REP

    reg mental_health School Stay Mask business travel emp infections deaths repub i.Time i.States mental_health_L1 mental_health_L2 mental_health_L3 mental_health_L4 if repub ==0
    estimates store DEM

    coefplot US DEM REP, keep(Mask Stay School) xline(0) recast(bar) ciopts(recast(rcap)) citop barwidt(0.1) levels( 95 90)


    3rd:

    gen Maskdays_L1 = Mask[_n-1]*13
    gen Maskdays_L2 = Mask[_n-2]*13
    gen Maskdays_L3 = Mask[_n-3]*13
    gen Maskdays_L4 = Mask[_n-4]*13
    gen Staydays_L1 = Stay[_n-1]*13
    gen Staydays_L2 = Stay[_n-2]*13
    gen Staydays_L3 = Stay[_n-3]*13
    gen Staydays_L4 = Stay[_n-4]*13
    gen Schooldays_L1 = School[_n-1]*13
    gen Schooldays_L2 = School[_n-2]*13
    gen Schooldays_L3 = School[_n-3]*13
    gen Schooldays_L4 = School[_n-4]*13


    reg mental_health i.States i.Time School Stay Mask business travel Maskdays_L1 Maskdays_L2 Maskdays_L3 Maskdays_L4 Staydays_L1 Staydays_L2 Staydays_L3 Staydays_L4 Schooldays_L1 Schooldays_L2 Schooldays_L3 Schooldays_L4 repub emp deaths infections
    estimates store US

    reg mental_health i.States i.Time School Stay Mask business travel Maskdays_L1 Maskdays_L2 Maskdays_L3 Maskdays_L4 Staydays_L1 Staydays_L2 Staydays_L3 Staydays_L4 Schooldays_L1 Schooldays_L2 Schooldays_L3 Schooldays_L4 repub emp deaths infections if repub==0
    estimates store DEM

    reg mental_health i.States i.Time School Stay Mask business travel Maskdays_L1 Maskdays_L2 Maskdays_L3 Maskdays_L4 Staydays_L1 Staydays_L2 Staydays_L3 Staydays_L4 Schooldays_L1 Schooldays_L2 Schooldays_L3 Schooldays_L4 repub emp deaths infections if repub ==1
    estimates store REP

    coefplot US DEM REP, keep(Mask Stay School) xline(0) recast(bar) ciopts(recast(rcap)) citop barwidt(0.1) levels( 95 90)

    I thought the issue was that the moving average was in days and the lags were a proportion of days. However, when converting to days by multiplying by 13 nothing changed.

    Again please help !
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