From my experience interviewing heroin addicts under the age of 40.....they almost universally started on oxy....then when oxy was reformulated so it could not be smoked...they moved to Percocet then heroin.
That’s been the transition here in Wi too. Oxy also became more expensive with the crackdown and heroin became the low cost alternative.
Mark Belling spent a few shows talking about it recently. Shocking hoe prevalent it’s become in the metro suburbs of Milwaukee