getting top 10% as a dummy variable

[Umair khan]

My apologies for very basic question.

I want to sort by year and create a dummy variable that will take a value of 1 if the value of the variable is in top 10% in that year and zero otherwise.

Many thanks for your help.

[Nick Cox]

You can use egen to get the 90th percentile by year.

[Charlie Joyez]

Umair, here's an example detailing Nick advice.

sysuse auto.dta,clear

bysort foreign : egen pc90_price=pctile(price) ,p(90)
gen top10=(price>pc90_price)

bysort foreign : tab top10
drop pc90_pric

To adapt this example to your issue, simply replace foreign by year and price by the variable you want to sort. top10 is your dummy variable.

[Umair khan]

Thanks Nick and Charlie for the quick Response.
Many thanks Charlie for the code.

[Nick Cox]

In practice you need to watch out for missings too.

gen top10=(price > pc90_price) if price <  .

[Umair khan]

Thanks Nick.