original data (see List and Rasul 2011) casts doubt on whether that conclusion was accurate for the actual experiments at the Hawthorne plant.<sup>26</sup> The first clearly and individually randomized social experiment was the Cambridge-Somerville youth study. This was devised by Richard Clarke Cabot, a physician and pioneer in advancing the field of social work. Running from 1942-45, the study randomized approximately 500 young boys who were at risk for delinquency into either a control group or a treatment group, the latter receiving counseling, medical treatment, and tutoring. Results (Powers and Witmer 1951) were highly disappointing, with no differences reported. Sociology and criminology continued to be early adopters in the use of random experimentation, with studies by Reimer and Warren (1957) on parole caseload levels, by Hanson and Marks (1958) on interviewer accuracy in the 1950 US Census, and by Ares (1963) on the large-scale Manhattan bail project.

In many ways public health acts as medicine on a social scale, and we find a similar trend for attempting to use randomization when possible even in large-scale interventions – starting a couple of decades later. A noteworthy early example involved testing the effectiveness of Jonas Salk’s polio vaccine in the early 1950s, when there was a debate about whether to implement comprehensive vaccination. In order to evaluate its efficacy (and its potential risks), given that the disease had a relatively low incidence rate (especially for so-called paralytic polio), a large sample was needed: in this case over a million children. Some local health departments were hesitant to randomize and preferred an approach in which all second-graders would be vaccinated, with the first- and third-graders serving as controls. Other health departments felt that this would not be sufficiently rigorous and therefore not sufficiently compelling, thereby wasting all the money and effort spent, so they preferred a randomized (double-blind) placebo approach. In the end about half of the participants ended up using each method, which illustrates some common difficulties of using RCTs in the field. Results (see Francis 1955, but also Meier 1972 for a broader perspective) were highly encouraging, and polio vaccination has been standard ever since.<sup>27</sup> Unfortunately but perhaps unsurprisingly, even convincing evidence of an effective and inexpensive vaccine has not yet led to the complete eradication of polio, which as of today still exists in the wild in Afghanistan, Nigeria, and Pakistan.

Another impressive early randomized experiment in the realm of public health involved family planning in Taiwan, China (see Population Council 1963 for the experimental design and Takeshita 1964 for results). The city of Taichung was divided into three roughly matched sectors, each of which consisted of hundreds of neighborhoods (of 25-30 families). Individual neighborhoods were randomized into either a control treatment; a treatment involving information by mail only; or one of two more exhaustive treatments (which included group meetings and personalized home visits), either with the wife only or with both spouses. The relevance of the sectors is that the percentage randomized into the exhaustive treatments differed across sectors, from 20% up to 50%. This allowed the researchers to look at intensity of treatment and to examine what they called “circulation effects” (i.e. spillovers), an extraordinarily

> 26 The potential existence of the Hawthorne effect may itself argue against some forms of randomized assignment and in favor of less formally rigorous but less disruptive techniques.

> 27 Modern vaccines, however, use live virus as opposed to Salk’s killed virus.

16