[Nick Cox]

If your variable is long then

gen wanted = floor(whatever/1000)

See also https://journals.sagepub.com/doi/pdf...867X0400300413 and https://journals.sagepub.com/doi/pdf...867X1801800311

[Clyde Schechter]

On the assumption that your postal code variable is numeric:

gen wanted = floor(postal_code_variable/1000) if postal_code_variable <= 55000