Discounting or Duty? Two Ways of Weighing Future People

Discounting values future welfare less than present welfare at a fixed annual rate, while rights-based and sufficientarian duties hold that present people owe future persons a determinate share of basic goods and a safe environment, whatever that rate happens to be. Suppose a policy averts a flood that will kill a thousand people in the year 2125. At a three percent annual discount rate, that loss enters the cost-benefit ledger at roughly five percent of its face value. Carry the same logic to 2225 and the figure falls below a third of one percent. Nothing in the calculation is hidden. It is simply compound interest applied to human lives, and it is the reason a modest-looking rate can make a catastrophe nearly invisible on a spreadsheet.

The Arithmetic of Patience

The defense of discounting is older than climate science. Frank Ramsey, writing in 1928, treated the discount on future utility as a moral failing to be eliminated, a sign of the imagination's weakness, yet he accepted that pure time preference could not be removed from a real economy. Later economists made it a working parameter. Their case is respectable: capital earns returns, future generations will likely be richer, and a dollar spent on a poorer present may do more good. The rate is a way of expressing how much we expect the world to change. The trouble is that the same rate does two jobs at once. It encodes an empirical bet about growth and a moral bet about whether distance in time dilutes claims. Nicholas Stern's 2007 review set its rate close to zero and was attacked for it; William Nordhaus, defending a rate near four percent, was accused of treating the climate's future as a commodity market. Partha Dasgupta argued that discounting climate damages cannot be settled by market rates alone, because the people bearing the cost have no seat at the market. The dispute is less about numbers than about who is counted as a party to the bargain.

A discount rate is a verdict on the future delivered in advance, and the people who would appeal it are not yet born.

Duties That Refuse to Compound

Rights-based approaches start from a different place. They do not ask how much a future harm is worth today; they ask whether a present action violates a claim that a future person holds. Henry Shue's distinction between subsistence and luxury emissions, first drawn in 1993, is the sharpest instance: emissions needed to meet basic needs carry a different moral standing from those that fund avoidable excess, and the wealthy cannot discount away a duty to avoid pushing future persons below a threshold of livable conditions. Sufficientarianism pushes the same intuition in a more modest direction. Harry Frankfurt's 1987 argument that what matters morally is having enough, not being equal, implies that the target for future generations is adequacy. The duty is not to maximize their welfare, nor to match ours, but to leave them above a floor. Because the floor is absolute rather than weighted, it is indifferent to the rate at which we would otherwise have shrunk its importance. | Feature | Discounting | Rights-based and sufficientarian duties | |---|---|---| | Unit of concern | Aggregate welfare, weighted by time | Individual claims and minimum thresholds | | Effect of distance | Reduces moral weight geometrically | Leaves the duty undiminished | | Treatment of rate | Central parameter | Irrelevant to the core duty | | Typical danger | Trivializes distant catastrophe | Hard to trade off against present gains | | Key source | Ramsey (1928), Nordhaus (2008) | Shue (1993), Frankfurt (1987) |

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Where the Two Camps Actually Disagree

The rights view has its own weakness. Thresholds are blunt instruments. If a duty is to keep future people above a floor, the present still needs a method for deciding how much present sacrifice that floor requires, and that question reintroduces tradeoffs the rights language was meant to avoid. A critic can fairly say that rights-talk relocates the arithmetic rather than abolishing it. Still, the disagreement is clarifying. Discounting treats future people as claims to be priced. The rights and sufficiency views treat them as parties who can be wronged. Edward Page's work on climate justice presses that second picture hard, arguing that the harms are not reducible to a loss of aggregate utility but are violations of entitlements the present is able to respect. Whether one accepts that depends on whether a century is an interval of accounting or a stretch of time in which real people will have to live.