total value stems from non-market uses of the marine resources (e.g., for swimming, recreational fishing, boating, wildlife viewing). Furthermore, the studies that have been done have consistently concluded that non-use value comprises a significant share of total value. In other words, people are willing to pay significant amounts for water quality improvements even when they do not directly use the waterbody. Although non-use values are particularly difficult to measure and the techniques used to measure them are controversial, available data is consistent in showing that non-use values are important. Thus, estimates of economic impacts that fail to include non-market benefits, including non-use values, are likely to significantly underestimate total economic impacts.

recently developed methodologies that combine information from both types of approaches in an effort to improve benefit estimates (Cameron 1992; Adamowicz et al. 1994, 1997; Englin and Cameron 1996; Huang et al. 1997). Combining the two approaches has the potential to increase the reliability of the estimates, although a possible inconsistency in the use of joint estimation exists (Huang et al. 1997). It also allows a decomposition of total value into use and non-use values. A study by Huang et al. (1997) combines stated and revealed preference models in the estimation of the willingness to pay for improvements in water quality in the Albemarle and Pamlico Sounds of North Carolina. While they do not provide measures of aggregate value, their results do show that non-use value constitutes a significant portion (over half) of total value. Bockstael et al. (1989) also found significant non-use values in their study. This suggests that ignoring non-use values will lead to significant under estimation of the total value of a water quality improvement (Box 4-3).

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