Without any data and based on the juniors I met, they pour out way more bugs right out of the gate and the code becomes really bad if not kept in check. That's

Without any data and based on the juniors I met, they pour out way more bugs right out of the gate and the code becomes really bad if not kept in check. That's a substantial difference between a junior and a senior. Of course this is dependent on technology and company onboarding and the codebase, so it's really haed. But also a junior comes trained in one programming language, maybe two, and you encounter many different requirements that might exclude juniors. For example Company uses Elixir, no junior is trained in that, a senior polyglot will learn very fast,a junior might have problems.