The collateral received for minting USDs is invested in other audited decentralized projects to generate organic yield. Currently, USDs collateral is earning yield on Curve Finance in the form of CRV tokens and swapping fees from the curve pool. This yield is shared between USDs holders and SPA stakers (The split is 50% for USDs holders and 50% for SPA stakers, but this share can be changed through governance). The yield share of USDs holders is used to purchase USDs from the open market, and the purchased USDs is distributed to USDs holders, directly into their wallet.