Other evidence in support of chemically induced carcinogenesis has been demonstrated by comparing cancer incidences in different parts of the world. Some cancers are more prevalent in certain geographical locations. For example, there are significantly higher rates of cervical cancer in developing nations (e.g., Latin America, Africa) but higher incidence of prostate cancer in developed countries ( Parkin et al., 2002 ). Gastric cancer is relatively rare in the United States but common in Japan. Studies over two generations of Japanese immigrants to the United States found that patterns of cancer development became similar to those prevalent in Western society. This change implicates environmental factors in the pattern of cancer development.