Gary Stevenson's 2019 answer, in one sentence: when wealth concentrates into few hands, more money flows to people who want to own assets rather than consume — bidding up scarce assets relative to wages and pushing their yields down. This page rebuilds that proposed mechanism step by step, with the thesis's model running live so you can test what follows from its assumptions.
After the 2008 crash, policy rates across the developed world fell to nearly zero. Through the decade in which Stevenson wrote, financial markets repeatedly predicted they would soon return to "normal". Those forecasts repeatedly proved too high. Stevenson's favourite example: in September 2014, the governors of the US Federal Reserve — the people who set the policy rate — predicted where it would be over the next three years. Not one of the governors, for a single year, guessed too low. All of them were wrong, by a lot, in the same direction.
Meanwhile asset prices did the opposite of what cheap-money-is-temporary thinking implied: UK houses, UK farmland (roughly doubling in price per acre between 2007 and 2016), and stock markets (the S&P 500 growing over 12% a year from 2009, before dividends) all raced far ahead of wages.
Stevenson's starting point is simple: when the smartest, best-incentivised predictors in the world are unanimously wrong for a decade, they are missing a cause. His candidate for the missing cause is rising wealth inequality. He has some standing to say so — as an interest-rates trader he bet, against the consensus, that rates would stay low precisely because inequality was rising, and in 2011 became his bank's most profitable trader in the world. The thesis is his attempt to turn that trading instinct into formal economics.
This is the key that unlocks the whole thesis, and it needs no maths.
Suppose a house earns £10,000 a year in rent. If the house costs £100,000, an investor earns 10% a year. If buyers bid the same house up to £500,000, the same £10,000 of rent is now only a 2% return. Nothing about the house changed — its effective yield fell purely because the price rose.
This is the thesis's effective interest rate: the income an asset pays divided by its price — a rental yield, dividend yield or comparable return. Bank Rate and the federal-funds target are policy rates, chosen by central banks. Policy rates influence borrowing costs and market yields, but they are not identical to the model's payout-to-price calculation. Stevenson connects the two through economy-wide saving and asset demand; the toy model directly solves only the asset yield.
That turns two features of the post-2008 decade — expensive assets and unusually low market returns — into one question: why was so much money chasing assets that buyers accepted very little income for holding them?
Economists test ideas by building tiny artificial worlds and seeing what happens inside them. Stevenson's world is deliberately as simple as possible, resting on three deliberate design choices:
The world contains consumption goods (food, haircuts, holidays) and a fixed stock of assets — think of it as land. Crucially, you cannot turn one into the other: no amount of saved wages manufactures a new plot of prime London. In most economic models saving automatically creates new capital, which quietly makes it impossible for asset prices to detach from everything else. Stevenson removes that assumption, because the decade after 2008 — savings piling up, interest rates at zero, companies buying back shares rather than building — looks exactly like a world where saving does not smoothly create new assets.
Give a struggling family an extra £1,000 and they will spend nearly all of it. Give a billionaire an extra £1,000 — or an extra million — and they will spend almost none of it; it gets saved, i.e. used to buy assets. This is well supported by evidence, and it is the engine of the whole thesis. In the model it is built in mathematically: people get satisfaction not just from consuming, but from owning wealth itself, and the desire to consume satiates while the desire to hold wealth keeps going. “Satisfaction from wealth” can stand for security, status, control, future options or leaving assets to heirs. It is a modelling assumption about why accumulation may continue after consumption needs are met — not a moral diagnosis of rich people.
Society is split into a rich group and a poor group. A single dial, E (for Equality), sets what fraction of society is in the rich group — and the rich group owns all the assets, split evenly among themselves. E = 1 means everyone owns an equal share (perfect equality). E = 0.05 means 5% of the people own everything. Everybody works the same amount either way. Crude — but it lets you turn inequality up and down like a thermostat and watch what happens.
Turn E down — concentrate the wealth. Each rich person now owns more, so each rich person is further into "spends almost nothing of each extra pound" territory. Society's total income hasn't changed, but more of it now flows to people who want to hold wealth with it rather than spend it. So more buying power chases the same fixed stock of assets. There is only one way that can resolve:
Below is not an illustration — it is Stevenson's model, solved in your browser using the equations from the thesis. Drag the equality dial and watch asset prices (as a multiple of wages) and the effective asset yield respond.
The left-hand side of the chart is the whole story. As E heads towards zero — wealth concentrating into ever fewer hands — the asset-price-to-wage ratio doesn't just rise, it takes off towards infinity, and the asset yield collapses towards zero. And it accelerates: each step of further concentration has a larger effect than the last. These curves show what follows inside the chosen model. If its assumptions capture an important force in the real world, the mechanism offers one explanation for persistent pressure on asset prices relative to wages and for low asset yields.
The wrinkle on the right, and how the thesis irons it out. In Model 1 you may spot that at high equality (E near 1) the curve can gently tip the "wrong" way, depending on the capital-share slider. Stevenson diagnoses this as an artefact of a crude assumption — Model 1 hard-wires the poor to spend everything, so as E rises, poor people "flip" into rich savers, which nudges prices up. Switch to Model 2, where everyone has the identical psychology and the rich save more only because they have more: the wrinkle vanishes. More equality then means cheaper assets and higher asset yields, smoothly, everywhere, for any capital share — even when the assets pay no income at all. The fix makes the result stronger, not weaker.
The thesis reads as four separate models, but it is more intuitive to see it as one claim surviving three rounds of objections — each model built to answer the sceptic's next question.
Expensive assets need not be a temporary bubble. If concentrated demand for scarce assets is an important force, high prices relative to wages can be an equilibrium of an unequal economy, not merely froth waiting to pop. That does not mean prices cannot fall; it means inequality supplies a persistent source of demand that a bubble story alone misses.
Low long-run asset yields become less mysterious. The model does not say a central bank can never raise its policy rate — the post-2021 cycle shows that it can. It says that, while wealth remains concentrated and scarce assets remain desirable, competition to own them can keep their prices high and their income yields low.
The spiral. In Stevenson's mechanism, inequality raises asset prices; higher prices increase owners' paper wealth and make it harder for workers without inherited wealth to acquire claims on future rent, dividends and other capital income. That can reinforce inequality. Stevenson points to falling UK home ownership and warns that the endpoint could be a society where inheritance matters more than work — what he calls a new feudalism.
The policy question widens. If this mechanism is empirically important, housing supply, credit conditions and monetary policy are not the whole story; the wealth distribution also belongs in the diagnosis. The thesis argues for measuring and testing that channel. It does not derive a particular tax or housing programme.
Being fair to the argument means being clear about its edges — most of which Stevenson flags himself.
None of these breaks the core intuition. They mark the distance between "here is a coherent, worked-out mechanism the profession has ignored" — which the thesis delivers — and "this is proven to be the cause" — which it does not claim.