[Joao Santos Silva]

If your variables do not have enough variation, they will drop out.

[diana amaya]

Thanks,

Only two exporting countries in my dataset account for 95% of the imports in the country of interest. Could this be the problem? If I run a model with only these two countries distance drops from the equation.

[Joao Santos Silva]

Distance drops whenever we include pair fixed effects. Notice that this is not a problem because the FEs account for the distance effect.

[Emmanuel Inyang]

Dear Prof. Joao Silva,

I want to estimate the bilateral trade flow (import and export) between Nigeria and 14 ECOWAS using PPML.

I need help on how to start the analysis using PPML

Please help out. Thank you.

[Joao Santos Silva]

See if this or this help.

[Emmanuel Inyang]

Dear Prof. Joao Silva,

Thank you for your response.

I used these commands, and I got this error message:

ppml tradeflow_comtrade_o contig rta Indistcap Ingdp_o Ingdp_d Inpop_o Inpo
> p_d
variable Indistcap not found

[Joao Santos Silva]

That means yo do not have a variable with that name in your dataset.

[Emmanuel Inyang]

Dear Prof.

I have that variable, and it showed when I did my descriptive statistics. It showed the same error for Ingdp_o, which was also part of the variables.

Is there something I am not doing right? Or is there how to fix it, please?

[Joao Santos Silva]

You have distance and gdp, but not their logs; you need to create them.