This is an interesting question! Not counting gear or everyday undergarments/socks/hosiery, I'd say 80% of my closet was purchased via secondhand/intermediary sellers: eBay, Poshmark, Goodwill, local consignment, and FurKids (a local thrift store that supports no-kill animal shelters).
Of these purchases, at least 65% was new with the tags still on. The remaining 30% or so appeared to be unworn or maybe worn once and cleaned or laundered. The remainder is true antique/vintage, dating from the 1910s to 1990s. I have a blouse that is 100 years old, that I will occasionally wear.
That's 80% of my wardrobe. The remaining 20% is split between items that I purchased new, or vintage and antique items I've inherited or been gifted.