Good point. That said, in many countries employee protection is solid enough that people would not need to worry. If within the EU, then GDPR regulations could also lead to pretty massive fines if a supposedly anonymous survey turned out not to be.
Interesting. Looks like a rising trend since the last financial crises. The effect of corona seems to be limited to a dip around the beginning of the pandemic, presumably due to uncertainty. No great resignation wave though, judging by the graph.