PRINCIPLE
4. ORIGINAL VS. SECONDARY DATA SOURCES
Time and resource limitations will also affect your ability to assemble the appropriate research materials. Will you have sufficient time and library access to perform a full review of the existing literature, or will you only be able to examine the materials you happen to have at hand?
Will you collect original data, or will you draw on data from existing studies?
To provide the information your client will need, your background materials and data sources will take many forms and will come from a variety of sources. All data have their limitations. One of the major skills you should develop as an analyst is determining when you are using data or existing findings in legitimate ways, and when you are using them in ways for which they were not intended and are not suited. This rule applies both to data that you use from other sources and to data that you collect yourself: in either case, the data may not fit your purposes exactly, and you will need to determine whether imperfect data are better or worse than no data.
Collecting original data sounds like it would be superior to using other people's data, but that superiority depends, as in so much in policy analysis, on the time, expertise, and resources available to you. Collecting data can be very expensive and time-consuming, and getting worthwhile results requires careful planning on how to gather the information. If your resources are limited, you are likely to be better off using existing studies
and data as much as possible. If, however, you cannot identify any prior studies of your subject of interest, you have a choice of either obtaining the necessary resources to conduct the study on your own, or you can try to extrapolate from existing research that is not directly related to your study.
For example, suppose you are studying the effects of timber harvesting on elk herds in Idaho, but the only existing research you can find is on the effects of timber harvesting on deer in Wisconsin. You could commission a team of biologists to study the effects of timber harvesting on elk in Idaho; that study might take one or more years. Alternatively, you may try to extrapolate some useful information from the Wisconsin deer study.
In that case, you need to determine whether deer and elk are likely to respond the same way to timber harvesting, and whether timber harvesting in Idaho is likely to have similar effects on wildlife as timber harvesting in Wisconsin. Are there scientific reasons that the deer data might provide an upper or a lower bound on effects on elk, or that Wisconsin data are likely to be higher or lower than Idaho data? Having some ability to compare between data sources may provide you with information and understanding that you previously did not have.
The same problem can arise with data that you generate yourself if your time or budget do not permit you to gather the "right" data. For instance, suppose that you would like to survey people on their attitude toward protecting air quality over Voyageurs National Park in Minnesota, but you only have the time and resources to ask people in your city. Will your sample of local people give you answers representative of those of people in other regions? Are you better off working with this sample, or extrapolating from existing research?
There are no general answers to these issues; the answer will depend on the level of existing research, on your ability to conduct a study, and, again, the need to get the most precise answer possible. You should discuss carefully with your client the advantages and disadvantages of existing work compared to new data sources, and the limitations resulting from your study however you develop it.
Avoiding extinction of endangered species is a source of existence or passive use value, defined as the benefit from knowing a resource exists even if no use is made of it. People who do not fish, participate in river recreation, or eat salmon may still pay something for a river with native or wild salmon. Passive use values are public goods, since these benefits can be simultaneously enjoyed by millions of people across the country (Loomis,
1996a). Wild stocks of Snake River Salmon have passive use value.
Passive use values can be estimated using the contingent valuation method (CVM; see Chapter 9). Unfortunately, CVM surveys take months to do and can cost up to $500,000. How can an analyst address this topic without doing an original study? Benefit transfer, "...the transfer of existing estimates of nonmarket values to a new study [site] which is different from the study for which the values were originally estimated" (Boyle and Bergstrom, 1992:657), was developed for just such purposes.
There are three approaches to benefit transfer: (a) use one estimate from a study that closely matches the application; (b) take an average of point estimates from related studies; or (c) transfer a benefit function such as a demand curve or willingness to pay equation (Loomis, 1992).
Loomis (1999) used these three approaches to transfer benefits from the existing literature to estimate the change in existence value from removing dams for restoring salmon populations in the Lower Snake River. While none is perfect, they suggest a likely range of values for restoring salmon.
One approach, using (a) above, matched the change in salmon populations due to dam removal to an existing study that valued a similar size change in salmon (Loomis, 1996b). The resulting lower estimate of the gain in passive use value would be about $205 million per year to non-user households in the Pacific Northwest and California. Another approach, using (b), took a simple average of estimates from the literature. The result estimates the net gain of dam removal as $261 million per year.
The (c) approach estimated a willingness to pay (WTP) function for salmon from four studies of West Coast residents' WTP for increasing salmon populations. From these studies, dam removal is estimated to produce $1,277 million in annual passive use values.
Two of the three estimates are quite close ($205 and $261 million), while the third approach results in a much larger estimate. Nonetheless, the three approaches allow the analyst to bracket the likely magnitude of passive use values for salmon in the Snake River without doing an original survey.
Since passive use values for increasing endangered salmon in the Snake River are certainly greater than zero, the benefit transfer approach avoids omission of this category of benefits. Omission is often taken as an implied zero value.
Box 2-2. Benefit Transfer and Passive Use Values of Wild Salmon