[Clyde Schechter]

Yikes, another typo! Here's the whole thing, corrected:

// VERIFY EACH COMBINATION OF industry_id, firm_id, & year
// OCCURS ONLY ONCE TO AVOID DOUBLE COUNTING
isid industry_id year firm_id, sort 

// COUNT NUMBER OF FIRMS IN EACH INDUSTRY IN EACH YEAR
by industry_id year (firm_id): gen firm_count_this_year= _N

// IDENTIFY SMALLEST NUMBER OF FIRMS IN ANY YEAR FOR EACH INDUSTRY
by industry_id (firm_count_this_year), sort: gen least_number_firms_any_year = firm_count_this_year[1]

Sorry about that.

[Issa Almaharmeh]

I run the regression however the new generated variable ''nds'' contains no data.

[Nick Cox]

It's your call. Either you relax the threshold of how many observations are "enough" for multiple regression or you need to rethink the analysis.