The use of calendar time as a basis for evaluating experience has both the advantage and disadvantage of being simple. The estimated cost of a project using personnel with low (median of 6 months) language and tool experience is 11 percent higher than the cost of using personnel with a nominal (median of 1 year) level of experience.

Other models estimate similar costs. For example, the Jensen-SEER model (Jensen and Lucas, 1983) and the Softcost-R model¹ have cost drivers comparable to the COCOMO TOOL and LTEX cost driver, with cost differentials in the range of 10 to 12 percent per rating level. Checkpoint has a "CASE tools" cost driver, with cost differentials varying from 10 to 15 percent per rating level, depending on interactions with other cost drivers covering staffing, methods, and language level (Jones, 1996d).

A recent sample of 25 Ada projects from the Air Force Cost Analysis Agency indicates an average TOOL rating for the level of tool support of "nominal" and an average LTEX rating for the level of language and tool experience support of "high." As discussed in Chapter 5, the committee's recommended strategy for DOD's investment in Ada tools is to invest at the margin with tool suppliers to develop tools with clear benefits that otherwise would not be built. With this investment, the level of Ada tool support likely would increase by one TOOL rating level over the next 5 years. Without this investment, the level of Ada tool support would likely decrease with respect to the pace of surrounding technology. Thus, it is reasonable to assume that the net effect of the Ada investment would be an improvement of one-level on the TOOL rating scale, and a corresponding 8 percent cost reduction.

Another effect of the committee's recommended Ada investment strategy, discussed in Chapter 5, would be to stimulate education and training in Ada, again via collaborative investments with suppliers at the margin. Without this investment, it will be much harder 5 years from now to find sources of qualified Ada personnel, and the likely net effect will be a one-level decrease in the average LTEX rating for Ada projects. With the Ada investment, the likely effect will be an increase in the average rating. Thus, a conservative assessment of the net effect of the committee's recommended Ada investment would be an increase of one-level on the LTEX rating scale, and a corresponding 8 percent cost reduction.