volatility of the firm's equity(annualized standard deviation)

[Mouldi Ben Ammar]

Dear All,

Hope my msg finds you very well.

I have a panel data 252 observations (daily ) (id, date,prc,ret and shrout) noting that ret=daily % change.
Please , how i can generate/ calculate an annualized standard deviation .
Please find below an example of data structure .

Many thanks in advance

gvkey	date	prc	ret	shrout
1005	2-Jan-81	26.375	0.004762	906
1005	5-Jan-81	26.875	0.018957	906
1005	6-Jan-81	26	-0.03256	906
1005	7-Jan-81	23.875	-0.08173	906
1005	8-Jan-81	22.875	-0.04188	906
1005	9-Jan-81	22.5	-0.01639	906
1005	12-Jan-81	22.5	0	906
1005	13-Jan-81	22.375	-0.00556	906
1005	14-Jan-81	22.25	-0.00559	906
1005	15-Jan-81	23.5	0.05618	906
1005	16-Jan-81	25	0.06383	906
1005	19-Jan-81	24.625	-0.015	906
1005	20-Jan-81	24.25	-0.01523	906
1005	21-Jan-81	24.375	0.005155	906
1005	22-Jan-81	24.625	0.010256	906
1005	23-Jan-81	24.75	0.005076	906
1005	26-Jan-81	24.125	-0.02525	906
1005	27-Jan-81	24.125	0	906
1005	28-Jan-81	24	-0.00518	906
1005	29-Jan-81	23.75	-0.01042	906
1005	30-Jan-81	24	0.010526	906
1005	2-Feb-81	17.875	-0.06901	1133
1005	3-Feb-81	18.75	0.048951	1133
1005	4-Feb-81	19.375	0.033333	1133
1005	5-Feb-81	19.75	0.019355	1133
1005	6-Feb-81	18.625	-0.05696	1133

[Attaullah Shah]

gen year = year(date)

bys gvkey year: egen sd_daily = sd(ret)

gen sd_annual = sqrt(252)*(sd_daily)

[Mouldi Ben Ammar]

Thank you Attaullah.