Mobile homes have grown phenomenally in number—from approximately 170,000 in 1940 to more than one and three-quarter million units in 1967—with even greater growth predicted. In 1961 they comprised seven percent of all new housing. By 1966 this figure doubled to 14 percent and represented more than 75 percent of all new homes valued at less than $12,500. The predominant location of mobile home parks on the periphery of cities, combined with the fact that mobile home residents are on the average considerably younger than the general population, lends credence to the speculation that mobile homes are providing “instant suburbia” for young, upwardly mobile, married couples. Other factors raise questions with this interpretation, however, e.g., only 13 percent of mobile home residents compared with 41 percent of the nation's residents are employed in white collar occupations. The relatively short life span and rapid decline in value of mobile homes raises the spectre of a new type of transportable slum which could elude housing reforms by moving beyond the jurisdiction of urban governments.