Who owns $Spy?

Can you clarify who exactly owns the stock ticker $SPY, and what entity or entities are responsible for managing and issuing shares of this popular ETF? Are there any major shareholders or institutions that hold a significant portion of $SPY, and what implications does this have for investors seeking to diversify their portfolios? Additionally, are there any regulations or oversight mechanisms in place to ensure the transparency and accountability of $SPY's ownership and management?