This guarantees the constancy of the budget constraint and vastly simplifies the problem of how the consumer should adjust consumption over the life-time.
Although similar to the budget constraint in consumer theory, the use of the isocost line pertains to cost-minimization in production, as opposed to utility-maximization.
Many economists have voiced grave concerns over using inter-temporal budget constraint as a de facto definition or criterion for fiscal sustainability.
In consumer theory, the equation restricting an individual or household to spend no more than its total resources is often called the budget constraint.
