During the four decades that passed between implementation and abolition, almost 63,000 Swedes were rendered infertile, in many cases in response to pressure from the state and sometimes as a result of outright compulsion. Furthermore, it was chiefly those regarded as “unproductive” who were the targets of that social policy.

So it sounds like the vast majority wasn’t compulsory…

But in a few rare cases it was, which were likely when the patient couldn’t legally give consent considering the subject.

Quick edit:

Was also in the 1930s when there was less options for non permanent birth control.