Green states that passive strategies act as a "systematic algorithm" where "did you give me cash? If so then buy everything in proportion to its market capitalization." He notes that 85 cents of every retirement dollar now flows into these strategies. Because these vehicles receive "ungodly amounts of cash" daily (Vanguard raises Simplify's total AUM every week), there is a persistent, price-insensitive bid under the largest market-cap stocks. As long as net flows are positive, the indices are mathematically forced to drift higher. LONG the S&P 500 (SPY) to align with the dominant mechanical flow of capital. A reversal in flows (net redemptions) would trigger the algorithm to sell indiscriminately ("passive sell pressure"), though the trigger for this was asked but not answered in the provided text.