Changes occurring in neighborhoods over time. The neighborhood life cycle includes the phases of birth, early growth, maturity, and decline. Not all neighborhoods pass through them more quickly the others. Neighborhoods decline for several reasons. The physical aging and deterioration of the building structures as well as the aging of the population contribute to the overall decline. Architectural obsolescence also makes these neighborhoods less attractive. Other changes include the intrusion of a business or industrial area into the neighborhood detracting from its overall quality.