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Thread: Diff in Diff -> what is the minimum amount of treated observations?

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    Red face Diff in Diff -> what is the minimum amount of treated observations?




    Can I use Diff in Diff when I only have a single treated observation?
    The case is that I observe the changes of a tax reform on real estate sales on the real estate prices (measured by an index). If I used the Index as my dependent variable I do not fulfill the 3rd assumption of the OLS, as there is autocorrel.
    I suggested using the logged returns, which have a nice normal distribution and are not correlated. But if I use the log returns I can only mark a single observation on the date of the tax increase (quarterly data) as treated.
    I get a nice significant effect, a decent R^2 and good error term plots; nevertheless I dont know whether an event study can be made with jsut 1 treated observation.

    I hope you guys can help me, I am new here =)

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    Re: Diff in Diff -> what is the minimum amount of treated observations?


    Not following. So you have data for one time period, geographic area???


    Provide a little more info. please!
    Stop cowardice, ban guns!

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