DCE evidence in environmental cost-benefit analysis

Environmental cost-benefit analysis requires monetary estimates of benefits that standard market data cannot provide. DCEs are the gold standard for generating those estimates.

This article explains how to use DCE WTP estimates in environmental cost-benefit analysis, from single-study aggregation through to benefit transfer and Green Book compliance.

Ben White, 07.07.2026

The environmental CBA evidence gap

Government investment decisions in environmental programmes - flood defence, biodiversity offsetting, water quality improvement, air quality management - are evaluated using cost-benefit analysis. The Green Book requires that all significant costs and benefits are quantified and monetised where possible.

Environmental benefits - cleaner water, more wildlife, better landscape - are often not monetised because they are not traded in markets. This creates a systematic bias against environmental investment: costs are always quantifiable, benefits often are not. DCE studies close this gap by providing robust monetary estimates of environmental benefits that can enter the CBA alongside engineering costs.

How WTP estimates enter the CBA

The steps from DCE WTP estimate to CBA benefit are: (1) estimate mean and distribution of WTP per household per year; (2) multiply by number of affected households to get annual aggregate benefit; (3) discount to present value using the Green Book social discount rate (3.5% for years 0–30, 3.0% for years 31–75); (4) sum across all benefit categories to get total present value of benefits; (5) subtract total present value of costs to get net present value; (6) calculate benefit-cost ratio.

Benefit transfer is used when there is no original DCE study for the specific good being valued. Published WTP estimates from similar studies are transferred to the policy context using income adjustments, geographic adjustments, and scope adjustments. The reliability of benefit transfer depends on the similarity of the study and policy contexts.

The Green Book guidance explicitly acknowledges stated preference methods as appropriate for environmental valuation and references the Building with Nature evidence base - which includes many DCE studies - as a source of transferable WTP values.

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Conducting environmental CBA with DCE evidence in SurveyEngine

Step 1: Identify the benefit categories to be valued. For each environmental attribute affected by the programme, identify whether it can be valued by market methods (e.g. carbon pricing for carbon sequestration), by administrative values (e.g. defra biodiversity metric values), or requires DCE evidence.

Step 2: Design the DCE to cover all required benefit categories. If multiple benefit categories need DCE evidence, design a single study that covers all of them as separate attributes. Avoid running multiple separate studies that produce inconsistent estimates.

Step 3: Estimate WTP for each benefit category. Estimate marginal WTP for each attribute from the DCE model. Express WTP in annual per-household terms, consistent with the Green Book aggregation framework.

Step 4: Aggregate and discount. Apply the affected household count for each benefit category. Discount using the Green Book rates. Sum across benefit categories to get total present value of benefits.

Step 5: Present sensitivity analysis on WTP estimates. Include low and high WTP scenarios using the 95% confidence intervals from the model. Report the BCR under each scenario. If the project passes the CBA under all scenarios, the evidence is robust. If the BCR is sensitive to WTP assumptions, flag this for decision-makers.

Worked example - natural flood management CBA

A natural flood management (NFM) programme is evaluated using a CBA that combines market evidence (avoided flood damage costs) with DCE evidence for non-market benefits. DCE WTP estimates: reduced flood risk for at-risk properties = £124/property/year; improved recreational quality of restored floodplain = £28/household/year (within 5km catchment); biodiversity improvement (wetland creation) = £19/household/year (national existence value).

Aggregation: flood risk benefit (2,400 at-risk properties) = £297,600/year; recreation benefit (18,000 households) = £504,000/year; biodiversity benefit (280,000 national households contributing existence value) = £5,320,000/year. Total annual non-market benefit: £6.1M. Present value (30 years, 3.5%): £106M. Engineering cost: £42M. Total benefit including avoided damage costs (£28M PV): £134M. BCR = 3.19.