'F model statistic missing' when testing parallel trend

[yao xiang]

Hello everyone，

There was a birth policy implemented only in urban area in 2015,and I’m trying to test the parallel trend of birth rate between hukou==1(urban area) and hukou==0(rural area) in 2013/2014/2016 so as to do difference in difference.

Here is my statistic and code:

I tried DID first and the result was fine,but when it comes to test the parallel trend(xtreg), it shows a lot of blanks:

What might be the problem? If there is anything I don't make clear,please ask me.
Thank you so much.

[Carlo Lazzaro]

Yao:
if you really have 6 observations, any inferential procedure does not make any methodological sense.
About the balance between the # of observations and the # of predictors, see https://projecteuclid.org/euclid.aos/1176350710.

[yao xiang]

Yao:
if you really have 6 observations, any inferential procedure does not make any methodological sense.
About the balance between the # of observations and the # of predictors, see https://projecteuclid.org/euclid.aos/1176350710.

Thank you so much,Cario!