The first two studies were replications of studies already done with others, to test the value of web studies. The remaining studies are new. Benefit is measured in standard units that allow comparisons of alternative programs, for example years of life saved, and the best program is the one that yields the most total benefit for a fixed cost, regardless of how the benefit is distributed.
People care about equity as well as efficiency.
We call this greater preference for equity when one test can be offered to everyone the all-tested equity premium. If people think this way, then their concern for equity may depend on how the situation is described to them. Usually, we can find a broader population that includes the population in question, as well as others. If we call subjects' attention to the broader population, their judgments may reverse. The description of the population may alter how well distributed the test appears and, thus, affect preference for one test or another.