The highest agricultural incomes were earned by suburban units that were able to sell produce and sideline products in the nearby cities.[1] Under the responsibility system, household incomes depended on the number of workers in each household and the household's success in holding down production costs and in supplying goods and services to local markets.[1] Most of the rural families with the highest incomes – the "10,000-yuan households" – were "specialized households" that concentrated family efforts on supplying a particular service or good.[1] Many of these families owned their own equipment, such as trucks or specialized buildings, and operated essentially as private concerns.[1] An increasingly important influence on rural incomes in the mid-1980s was the expansion of nonagricultural rural enterprises, often referred to as "township enterprises."