Have US stock prices reached the limits of global investor flows?
Core argument: US equities need to attract roughly 65 cents of every dollar flowing into stocks to keep rising, with US market cap now about as large a share of global indices as any single country has ever been.
While the US is relatively unconstrained by economic limits, it faces limits of pricing that mean it would take almost a miracle for US assets to repeat the last decade. US equity pricing now implies not just cyclical outperformance, but the pushing back of structural limits. One example is the limit of flows: US market cap is now roughly as large a share of global indices as one country has ever been. To keep rising, US equities need to attract ~65 cents of every dollar that flows into stocks. But the pricing doesn’t make those flows attractive: in 2010, US earnings were discounted to grow modestly and at a similar rate to the rest of the world. The US then had an exceptional decade because its companies were more dynamic, had more supportive governance for shareholders, and operated against a more favorable policy backdrop. An AI productivity miracle could push back the limits and extend US outperformance, so we are tracking this closely. AI will shape the environment directly, both near term (through capex, winners and losers, etc.) and more broadly over time (e.g., productivity growth expanding the limits).


