In 2007, 22 Wake County, North Carolina traditional calendar schools were switched to year-round calendars, spreading the 180 instructional days evenly across the year. This paper presents a human capital model to illustrate the conditions under which these calendars might affect achievement. We then exploit the natural experiment to evaluate the impact of year-round schooling on student achievement using a multi-level fixed effects model. Results suggest that yearround schooling has essentially no impact on academic achievement of the average student. Moreover, when the data are broken out by race, we find no evidence that any racial subgroup benefits from year-round schooling. (JEL H75, I21, I28, J24)S ummer vacation, a much anticipated three-month break from school, has long been a staple of the US education system. Recent concern over tightening budgets and summer learning loss, however, has led to growing discussion over the merits of "modified" year-round school calendars. Such calendars spread the same number of school days over a longer period, effectively breaking up the long summer break into four or more smaller breaks throughout the year. 1 According to the National Association of Year-Round Education, over two million students attended a year-round school in 2007. 2 This number, about 4 percent of all US students, represents a marked increase from the 360,000 students (roughly 0.7 percent of all US students) who attended a year-round school in 1986. 3 While the number of year-round schools is on the rise, there is currently little consensus on the relative benefit (or cost) such a schedule affords. Rather, calendar conversions have 1 Thus, this type of year-round calendar is different from the "extended year" calendar, where the number of instructional days is increased.

In the face of school crowding and fears about inequalityinducing summer learning loss, many schools have started to adopt multi-track year-round school calendars, which keep the same number of school days, but spread them more evenly across the calendar year. This change allows schools to support a larger student population by rotating which students are on break at any point in time. While year-round schooling can save money, the impact on academic achievement is uncertain and only recently have large-scale studies become available for policy makers. This brief examines research on the effects of multi-track year-round schooling, focusing on two rigorously executed case studies. This research gives little support for claims that year-round schooling will boost student achievement. Except as a remedy for highly over-crowded schools, year-round schooling seems to have little impact on achievement, and has even been shown to decrease achievement, especially among the most high-risk student populations.

Developments in digital imaging and fluorescent microscopy provide a new method and opportunities for quantification of protein expression in human tissue. Archived collections of paraffin-embedded tumors can be used to study the relationship between quantitative differences in protein expression in tumors and patient outcome. In this report we describe the use of a DeltaVision Restoration deconvolution microscope, combined with fluorescent immunohistochemistry, to obtain reproducible and quantitative estimates of protein expression in a formalin-fixed paraffin-embedded tissue. As proof of principle, we used antibodies to the estrogen and progesterone receptors in a hormone receptor-positive breast cancer specimen. We provide guidelines for control of day-to-day variability in camera and microscope performance to ensure that image acquisition leads to reproducible quantitative estimates of protein expression. We show that background autofluorescence related to formalin fixation can be controlled and that for proteins that are expressed in nearly every cell, multiplexing two primary antibodies on the same slide does not significantly affect the results obtained. We demonstrate that for proteins whose expression varies markedly from cell to cell, data reproducibility, as assessed by imaging successive tissue sections, is more difficult to determine.

No abstract

When consumers choose to abstain from purchasing meat, they face some uncertainty about whether their decisions will have an impact on the number of animals raised and killed. Consequentialists have argued that this uncertainty should not dissuade consumers from a vegetarian diet because the "expected" impact, or average impact, will be predictable. Recently, however, critics have argued that the expected marginal impact of a consumer change is likely to be much smaller or more radically unpredictable than previously thought. This objection to the consequentialist case for vegetarianism is known as the "causal inefficacy" (or "causal impotence") objection. In this paper, we argue that the inefficacy objection fails. First, we summarize the contours of the objection and the standard "expected impact" response to it. Second, we examine and rebut two contemporary attempts (by Mark Budolfson and Ted Warfield) to defeat the expected impact reply through alleged demonstrations of the inefficacy of abstaining from meat consumption. Third, we argue that there are good reasons to believe that single individual consumers-not just individual consumers taken as an aggregate-really do make a positive difference when they choose to abstain from meat consumption. Our case rests on three economic observations: (i) animal producers operate in a highly competitive environment, (ii) complex supply chains efficiently communicate some information about product demand, and (iii) consumers of plant-based meat alternatives have positive consumption spillover effects on other consumers.