But average SPAC deal size is climbing, sparking hope for SPAC-based ETF issuer Mark Yusko that these new investment vehicles still have legs. "The size of an IPO, whether it's a traditional IPO or a SPAC, is absolutely a proxy for quality. And the size of the average SPAC has been rising. The size of the average IPO has been falling," the CEO and chief investment officer of Morgan Creek Capital Management told CNBC's "ETF Edge" on Monday. Morgan Creek helps run the Morgan Creek - Exos SPAC Originated ETF (SPXZ), an actively managed basket with two-thirds of its assets in post-merger SPACs. Its largest holdings are in U.S. Treasury bills, Paya Holdings and MP Materials. It also holds shares of 23andMe, Utz Brands and Virgin Galactic.