In economics, the cycle of poverty is the "set of factors or events by which poverty, once started, is likely to continue unless there is outside intervention." The cycle of poverty has been defined as a phenomenon where poor families become trapped in poverty for at least three generations, i.e., for enough time that the family includes no surviving ancestors who possess and can transmit the intellectual, social, and cultural capital necessary to stay out of or escape poverty; in calculations of expected generation length and ancestor lifespan, the lower median age of parents in these families is offset by the shorter lifespans in many of these groups.