Zero-based budgeting is a method of budgeting where all expenses must be justified for each new period, starting from zero, rather than using the previous budget as a baseline. It was developed in the 1960s and grew in popularity in the 1970s when adopted by the US government. The goal is to evaluate all expenditures and justify their inclusion in the budget, rather than assuming existing programs will continue to receive funding. While it aims to improve budgeting efficiency, zero-based budgeting can be time-intensive and its use has declined since the 1980s.