The nuclear family has been considered the "traditional" family since the communist scare in the cold war of the 1950s. The nuclear family consists of a mother, father, and the children. The two-parent nuclear family has become less prevalent, and pre-American and European family forms have become more common.[1] These include same-sex relationships, single-parent households, adopting individuals, and extended family systems living together. The nuclear family is also choosing to have fewer children than in the past.[3] The percentage of married-couple households with children under 18 has declined to 23.5% of all households in 2000 from 25.6% in 1990, and from 45% in 1960.