10 HIV survival and the introduction of HAART. In a journal article, Philipson and Jena (2006) study HIV survival and expenditures. Figure 13.9 shows trends in HIV survival and HIV expenditures in the US. a Figure 13.9(a) shows that HIV survival after diagnosis improved dramatically over a twenty-year period. Propose three explanations for this fact, one involving phar- maceutical innovation, one involving improved HIV screening, and one involving demographic changes in the at-risk population. It is okay if these explanations do not reflect actual historical developments, but they should explain why survival after diagnosis might be improving over time. b Suppose now that these curves have been adjusted for screening and demo- graphics, and that the survival improvement is entirely a reflection of techno- logical change (such as the introduction of HAART, an effective AIDS drug that boosts immune function, in 1994). Explain why we do not have enough informa- tion in Figure 13.9(a) to determine if the improvements in HIV longevity were cost-effective. c Figure 13.9(b) shows that expenditures on HIV treatment rose rapidly during approximately the same period. Is this evidence that the price of HAART wasTECHNOLOGY AND THE PRICE OF HEALTH CARE 277 (a) HIV survival curves, 1980-2000 1 0.9 0.8 0 . 7 0.6 Probability 0.5 0.4 1980 1986 1992 2000 0.3 0.2 0. 1 0 10 20 30 40 50 60 70 80 Years since infection (b) HIV expenditures, 1986-2004 4.5 4 3.5 3 2.5 $ billion 2 1.5 - 1 0.5 0 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year - Public - Private - Total Figure 13.9. Trends in HIV survival and expenditures in the US. (a) HIV survival curves, 1980-2000. (b) HIV expenditures, 1986-2004 Source: Figures 3 and 4 from Philipson and Jena (2006). Reproduced with permission of De Gruyter. increasing during this time? Is it evidence that the cost of survival was increasing during this time