The idea of a seven-year itch puts a specific time on the generally observed phenomenon that data sets of married people show a rising, then a falling, risk of divorce over time. However, statistical results from these data sets are very sensitive to the statistical methods used, and such patterns may just reflect the method, rather than any underlying reality. In samples taken from the U.S. National Center for Health Statistics, there proves to be an average median duration of marriage across time. In 1922 the median duration of marriage that ended in divorce was 6.6 years. In 1974 the median duration was 7.5 years. In 1990 the median duration was 7.2 years. While these can fluctuate from year to year, the averages stay relatively close to the seven year mark. Research from 2012 found that American divorce rates peaked after about ten to 12 years. Studies from China of marriages between 1980 and 2010 found that divorce rates peaked anywhere from 5 years to 10 years after marriage, with more recent marriages being more likely to divorce after shorter periods of time. Divorce rates in Finland as of 2018 show similar patterns, "consistent with psychological notions of ‘honeymoon’ and ‘seven-year itch’."
Media influences
The modern usage of the phrase gained popularity following the 1955 movie of the same name starring Marilyn Monroe. In the film, a man sends his family off on vacation for the summer while he stays back to work. He begins to fantasize about women that he previously had feelings for, when his new neighbor moves in and he decides to try and seduce her. Things go awry and he ends up not going through with it, but he believes that his wife will somehow know that he is trying to be unfaithful. Whilst the term was originally used for unfavourable conditions of a long duration, the talkie helped to popularize its usage to refer to the decrease of romantic feelings between married couples over time. The phrase has become so popular that some couples use it as an indicator of the lifespan of their marriage, a famous example being a Bavarian politician Gabriele Pauli, who has been divorced twice. She suggests after seven years marriage should end, with the couple required to resay their vows if they wish to continue for another seven years.