Serial monogamy is the couple model according to which a person has a single sexual partner at a time, which changes every certain period of time. Serial monogamy therefore implies relationships of fidelity but without long-term commitment. The phenomenon has been frequent since the end of the 20th century in advanced societies, driven by the economic independence of individuals that allows them to consider changing partners without endangering their economic well-being. The low birth rate, with a lower number of children per couple, in fact frequently without children, also facilitates the change of partner, by relaxing over time the commitment to raising children together. Individualism and the disappearance of the dogma of marriage for life, a consequence of secularization, has also facilitated the rise of the phenomenon.