average size had grown to 469 acres (Olenchock and Young, 1997a; U.S. Department of Agriculture, 1997). This change has also affected the prevalence of family farms and family labor. In 1940, 75.6 percent of all workers on farms were family members, defined by the U.S. Department of Agriculture as self-employed or unpaid family workers. This percentage had declined to 69.4 percent by 1995; see Figure 5-2. The results of changing farms and demographics of workers may yield new types of agricultural diseases and injuries (Olenchock and Young, 1997b), such as chemical and biological exposures, resulting in new acute syndromes or chronic conditions.
As the average size of farms continues to increase and more workers are hired, there will likely be fewer children and adolescents of the owners working on farms. However, there may be a subsequent increase in the number of adolescents hired as farmworkers and in the number of farmworkers' children who are working alongside their parents in the fields. The results of the National Agricul-