1. 263 US residents completed the study over the internet, making hypothetical choices between immediate and future monetary and environmental gains (within-subjects manipulation). The environmental scenarios described temporary or permanent improvements in air or water quality (between-subjects manipulation). Indifference points were imputed from a series of binary choices (“choice titration”) and fill-in-the-blank (“matching”) items. Discount factors (δ) were log and sign transformed to normalize outliers, especially some instances of negative discounting. The pattern of results was similar for air and water quality, so we have grouped them together here for our analyses. Pricing Out Environmental Outcomes Yields Lower Discount Rates David J. Hardisty & Elke U. Weber Columbia University Design Overview Abstract Discussion Contact: David Hardisty, http://davidhardisty.info, djh2117@columbia.edu Consistent with previous literature, larger magnitude outcomes (permanent environmental gains) were discounted less than smaller magnitude outcomes (temporary gains), and longer delays were discounted less than immediate delays (Frederick et al, 2002). Although environmental gains were discounted similarly to monetary gains when measured with a between- domain metric (ie, pricing them out), environmental gains were discounted much more when measured with a within-domain metric. Why? Perhaps when measured with dollars, participants are primed to think of alternate $ investments and market discount rates. Another possibility is that many participants are hesitant to trade off environmental values with money, asserting that an environmental benefit is equally valuable no matter when it is realized, thus translating to lower discount rates. Methods: Sample Questions References Introduction Results: Median Indif. Points 263 US residents from a range of demographic backgrounds considered hypothetical monetary and environmental scenarios with immediate or delayed outcomes (6 months or 2 years). When discount rates for environmental scenarios were measured through willingness-to-accept ("pricing out"), discount rates for monetary and environmental outcomes were equivalent. However, using a within-domain measure of discounting yielded much higher discount rates for environmental scenarios. Discount rates for environmental outcomes (and other non- financial outcomes, such as health or lives) are frequently measured using one of two different methods. A within-domain measure might have respondents compare an immediate environmental benefit with a potentially greater environmental benefit at different points in the future, computing the discount rate from the difference in benefits per unit of delay (Baron, 2000). In contrast, a between-domain measure might ask participants how much an immediate environmental outcome is worth to them, compared with how much it would be worth to them if it were delayed different amounts, then computing the discount rate from the difference in dollar amounts per unit of delay (Hammitt & Harvey, 2000). Little is known about the whether or how the measurement method chosen affects the imputed discount rates. Results Which option do you prefer? [Within-domain, monetary:] Receive $150 immediately ORReceive $195 six months from now [Within-domain, environmental:] Improved air quality immediately, for 28 days ORImproved air quality two years from now, for 36 days [Between-domain, environmental:] Receive $250 immediately ORPermanently improved water quality six months from now DomainDelayImmediate Value Future Value Money6 months$150 now$212 later Money2 years$150 now$302 later Env Temp6 months28 days now80 days later Env Temp2 years28 days now80 days later Env $ Temp6 months$120 now$70 now Env $ Temp2 years$120 now$35 now Env $ Perm6 months$3000 now Env $ Perm2 years$3000 now$700 now Between-Domain Measure of Discounting 0 0.2 0.4 0.6 0.8 1 1.2 $env$Tmpenv$Perm mean -ln(δ) 6 mo 2 yr Within-Domain Measure of Discounting 0 0.5 1 1.5 2 2.5 3 3.5 $envTmp mean -ln(δ) 6 mo 2 yr Frederick, S., Loewenstein, G., & O’Donoghue, T. (2002). Time Discounting and Time Preference: A Critical Review. Journal of Economic Literature, 40, 351- 401 Baron, J. (2000). Can We Use Human Judgments to Determine the Discount Rate? Risk Analysis, 20, 861-868 Hammitt, J. K., & Harvey, C. M. (2000). Equity, Efficiency, Uncertainty, and the Mitigation of Global Climate Change. Risk Analysis, 20, 851-860