I searched Stata help and this forum but found no solution. I want to calculate some simple ratios on panel data like Book Leverage = Liabilities (LT) / Total Assets (AT) getting this:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str61 Description str7 ID_S float qdate long(LT AT) float Book_Lev long(EBITDA SALES PPE)
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 203 146433000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 200 146229000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 198 139348000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 197 138153000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 199 136735000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 196 135862000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 194 131956000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 195 127187000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 193 119456000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 192 115449000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 189 114407000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 188 114190000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 190 113145000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 184 111548000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 191 110310000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 186 109690000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 185 109276000         . . . . .
"VOLKSWAGEN AG - TOTAL LIABILITIES" "D905009" 187 106606000         . . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 220         . 375827000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 221         . 374019000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 223         . 373909000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 222         . 371411000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 218         . 347308000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 219         . 345331000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 217         . 336124000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 216         . 333909000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 214         . 323398000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 212         . 321771000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 213         . 319092000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 215         . 318711000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 210         . 308973000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 211         . 301729000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 209         . 274958000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 208         . 264919000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 207         . 247293000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 206         . 228818000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 205         . 218175000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 204         . 213255000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 202         . 195734000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 203         . 195145000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 201         . 192960000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 200         . 188121000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 198         . 176784000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 197         . 174568000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 199         . 174165000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 196         . 172807000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 194         . 170631000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 195         . 164575000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 193         . 154627000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 192         . 149301000 . . . .
"VOLKSWAGEN AG - TOTAL ASSETS"      "D905009" 189         . 143284000 . . . .
end
format %tq qdate

The data is later to be used for panel regression on this quarterly dataset.

Thanks for sharing your thoughts.