difference-in-difference DiD

[hussein bataineh]

Hi

please i face problems in applying difference-in-difference

Independent Variable:
hard_final_Exact_new: This binary indicator variable is assigned a value of 1 if a firm freezes its defined benefit plan for all employees and 0 if it does not. In the event of a pension freeze, the value is coded as 0 for all years prior to the freeze and as 1 for the year of the freeze. All subsequent years after freeze are excluded from the regression analysis. if the firm face pension freeze it will take a value of 1 just one time in all its life and the subsequent years are excluded.
For example, if the sample period is from 2004 to 2022 and a pension freeze occurs in 2018, the variable is coded as 0 from 2004 to 2017, 1 in 2018, and the subsequent years are excluded.

Dependent Variable:

Continuous Variable


my sample is not large it is less than 4000 observations

can you please advice me where is the problem in DID that im facing

. xthdidregress twfe ( market_adjusted_return Firm_Size_w ROA_w Leverage_w Market_book_four_w Non_pension_CFO_w STD_CFO_w Board_Independence_w BoardSize_w Gender_Diversity_w Fund_Sta
> tus_w FUNDING_RATIO_w Platn_Size_w CSR_Committee SustainabilityScore_w)(hard_final_Exact_new ) , group(id) 
note: variable _did_cohort, containing cohort indicators formed by treatment variable hard_final_Exact_new and group variable id, was added to the dataset.
no room to add more variables
    Up to 5,000 variables are currently allowed, although you could reset the maximum using set maxvar; see help memory.
r(900);

end of do-file

r(900);