There is no single stock market. Capital arranges itself along a continuum of risk, from cash-flows-now at the bottom to long-duration disruption at the top.
The bottom of the curve: defensives, dividends, short-duration earnings. Paid now, low beta, low drama.
The top of the curve: speculative, long-duration, disruptive names. Paid in a future the market discounts heavily.
The slope between them is the risk premium, the extra return demanded to climb one notch higher.
That slope steepens and flattens as appetite shifts. The slope itself is the market's risk appetite, priced.
Gormsen & Lazarus 2023 'Duration-Driven Returns' · Stein 2013 'Overheating in Credit Markets' (reach-for-yield)