In Marxian economics and related schools, unearned income originates from the surplus value produced by an economy, where "surplus value" refers to value beyond what is needed for subsistence. As such, individuals and groups who subsist on unearned income are characterized as being in an exploitative relationship because the unearned income they receive is not generated by their effort or contribution (hence why their income is "unearned"). The existence of unearned income received on the basis of property ownership forms the basis for the Marxist class analysis of capitalism, where unearned income and exploitation are viewed as inherent to capitalist production.