Key Takeaways:
Renowned short-seller Carson Block is betting against the US corporate credit market, initiating a significant short position in two of the largest debt ETFs based on his thesis that an AI-driven unemployment shock will spark a wave of corporate defaults.
"In the next three to five years, you're going to see a significant number of companies replacing employees with some form of AI," Block, the founder and CEO of Muddy Waters Capital, said in a Bloomberg TV interview on March 31, 2026. He argued a single AI implementation could replace as many as seven workers.
Block disclosed he is using bear put spreads to short BlackRock’s iShares iBoxx High Yield Corporate Bond ETF (HYG) and its investment-grade counterpart, the iShares iBoxx Investment Grade Corporate Bond ETF (LQD). He anticipates that credit spreads will widen significantly as the market prices in the risk ahead of the economic damage fully appearing in employment data.
The trade pits Block against a credit market that has remained resilient even as concerns mount around private credit and rising interest rates. His thesis wagers that structural risks, including over-concentration in passive ETFs and liquidity mismatches between the funds and their underlying bonds, will amplify the coming shock and create a downward spiral when sentiment turns.
Block’s core argument is that the productivity gains from AI will translate directly into job cuts on a scale that will weaken the broader economy. He pointed to his own use of Anthropic's Claude AI to handle legal work as an example of the displacement already underway. "This is going to be replicated across industries," he said. The logical chain follows that mass layoffs will lead to higher unemployment and a weaker economy, which in turn will erode corporate revenues and their ability to repay debt, ultimately triggering a default cycle.
This view contrasts with the narrative that AI-related job losses are a distant problem. However, recent actions by major technology firms lend some credence to the theme of financial strain. Companies including Oracle, Microsoft, and Amazon have laid off tens of thousands of employees, not necessarily because AI has replaced their roles, but because the firms are cutting costs to fund multi-billion dollar investments in AI data centers—a massive capital expenditure cycle built on uncertain future returns [4].
Block is using bear put spreads, an options strategy that involves buying and selling puts at different strike prices, to define his risk. He referred to it as a "convex trade," designed to limit the cost of holding the position while offering significant upside potential if a sharp market downturn occurs.
Beyond the AI thesis, Block’s bet is also a critique of market structure. He highlighted the massive scale of passive investment in credit markets and the potential for a liquidity mismatch. Corporate bond ETFs like HYG and LQD offer daily liquidity to investors, but the individual bonds they hold trade far less frequently.
In a stressed scenario where investors rush to redeem their ETF shares, the funds could be forced to sell their underlying bond holdings into an illiquid market. This forced selling could drive bond prices down sharply, creating a feedback loop that exacerbates the very crisis investors are trying to escape. This concern is compounded by existing fragility in the $3 trillion private credit market, where recent failures have already put mainstream banks on edge [3].
The move by a high-profile short-seller puts a spotlight on the potential second-order effects of the AI boom, shifting the narrative from a pure productivity gain to a significant credit risk. If Block's thesis proves even partially correct, it could force a widespread re-pricing of corporate debt long before AI's full economic impact is understood.
This article is for informational purposes only and does not constitute investment advice.
