school places will yield a negative net social rate of return. The value of B such as nine years of school, vary according to economic conditions and will be controversial both because of difficulties in calculating debate over which types of social benefits should be considered. earnings gains and Figure 8.6 also illustrates the inherent conflict between optimal private a social investment strategies a conflict that will continue to exist as long as private and social valuations of investment in education continue to diverge as students climb the educational ladder.