1980s, Kane attributes its 1980-84 decline to the growth of direct college costs and their 1984-87 rebound to the strong growth in the average parental education of Afro-American youth. Analysing the impact of affirmative action admitting the use of racial preferences in college admissions, Kane observes that the use of such action seems to be limited to the most selective fifth of colleges and that the net relationship between college selectivity, earnings and college graduation rates is positive for minority and other students, going on to argue that colleges' student bodies wouldn't be as racially diverse without affirmative action. Importantly, Kane and David T. Ellwood find that the college enrollment rates of youth displaying similar levels of academic preparation for college still vary considerably depending on their parents' income and education, with the gaps having widened in the 1980s and 1990s due to the growth in the returns to college education. Finally, together with Christopher Avery, Kane has investigated the impact of Boston's College Opportunity and Career Help (COACH) programme, a programme that has Harvard University students help public high school students make career plans and submit college and financial aid applications, and found that (i) high school students tend to overestimate both the tuition rates and rates of return to college education independent of their socioeconomic background, (ii) that the complexity of the financial aid and college application processes often discourages low-income students even if they are qualified and interested in a college education, (iii) and that many public high school students reporting an interest in college education either don't believe they are qualified and/or never wanted to pursue college education anyway. Research on school accountability, competition, quality and charter schools Another substantial body of Kane's research addresses the topics of school accountability, school choice and quality, and the effectiveness of charter schools. With regard to school accountability, Kane and Staiger have been critical of test-based school accountability systems, arguing that the imprecision and volatility of school test scores (e.g. due to sampling variation or sample size-invariant idiosyncrasies) often used as a basis for such systems may weaken or pervert incentives. Instead, they advocate for extending rewards and bonuses even to schools without extremely high scores to effectively incentivize large schools, not making them contingent on improvements in each racial group to avoid disadvantages for integrated schools, to use improvements across both years and outcomes as a basis, and