Low income is determined by the federal government's "Department of Housing and Urban Development," which defines low income as income that "does not exceed 80 percent of the median family income for the applicable area." The applicable area's median family income is calculated by the same department.
This low income standard is created as a way of deciding which people and families are entitled to benefits from the Uniform Act. The Uniform Act was enacted in 1970 to provide help to people who needed financial help.
Low income is also subjective and what one person may see as a low income, another person may see as a substantial income.