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Age-Gap Algebra

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Numbers don't lie!

Jenny: I'm 8. That means that when I'm 18, you'll be 28. And when I'm 28, you'll be 38. [...] And when I'm 38, you'll only be 48. That's not much difference at all.
Edward: Sure seems like a lot now though, huh?
(twenty years later)
Edward: Your name's different. Did you get married?
Jenny: Yeah. I was 18, he was 28. Turns out it was a big difference.

One common criterion for compatibility between prospective marriage or romantic partners is the difference between their ages. This trope is when a specific formula or calculation is proposed to determine either the "ideal" age gap or the maximum allowable age gap before it becomes "creepy".

Traditionally, a man was expected to be established in his career and lifestyle before marriage, whereas a woman usually transferred directly from her father's household to her husband's within a couple of years of reaching adulthood, so it was considered ideal for the man to be at least somewhat older. As society changed, this became less and less the case, and in modern works a very small age gap is often considered ideal, with a maximum allowable (as opposed to "ideal") age gap proposed, and often applied equally in either direction (older man vs. older woman).

One commonly-applied formula is the "half your age plus seven" rule, in which the older partner's age is divided by two and then increased by seven to reach either the ideal or minimum allowable age for a romantic partner. This has the advantage of allowing for a larger age gap the older the partners get; the four-year age gap between a 14-year-old and an 18-year-old is significant (and not allowed by this rule), but the same age gap between an 86-year-old and a 90-year-old isn't worth comment. The rule would theoretically create a paradox for people under 14 because the younger partner would have to be older than the older partner, but 14 is about the youngest you can be and make anything even remotely resembling adultish decisions respecting relationships anyway, so this rule works out rather well. In its earliest appearances, this rule is often cited as having French origins, although this citation always seems to appear in English-language (British or American) sources, leaving its true origin mysterious.

Another, somewhat vaguer metric often cited is declaring an age gap creepy when a partner is "old enough to be your mother/father," carrying with it as it does implications of symbolic Parental Incest or Wife Husbandry. This would place the maximum allowable age gap at a static fifteen to twenty years or so, depending on if the speaker is referring to the physical ability to have children or the socially acceptable age.

Compare Age-Gap Romance, May–December Romance, Comedic Lolicon, Likes Older Women, Likes Older Men, and Wife Husbandry.

Examples in fiction:

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    Anime and Manga 
  • In Four Knights of the Apocalypse, 16-year-old Lancelot gets his first kiss stolen by the 12-year-old Guinevere, who claims to be his destined lover. He's very put off by her young age, but Guinevere points out her age won't be an issue in their future romantic relationship because both of them will be adults when it actually happens.
    Guinevere: I may be a kid now... But by the time you turn twenty, I'll be sixteen!

    Comic Books 
  • This is used to justify Bruce Wayne having a relationship with Superman's granddaughter (who is his own granddaughter by adoption) in the far-future sections of Superman & Batman: Generations III; both being past 400 years old makes them basically "the same age".

    Films — Live-Action 
  • Big Fish: While in the town of Spectre, Edward befriends a young girl named Jenny, who develops a crush on him. He's eighteen at the time and she's eight, but that doesn't put her off, as she says once she's eighteen he'll be twenty-eight and it won't be such a big difference. Twenty years later he meets her again and finds she's divorced from a previous husband, who was also ten years older than her. According to her, it turned out to be a big difference. As for she and Edward, they don't get together, because he's already married to his One True Love.
  • The main premise of Liberal Arts is about the Unresolved Sexual Tension between a 35 year-old man and a 19 year-old young woman. When the male lead is contemplating having a Relationship Upgrade with the female lead, he's seen calculating their sixteen-year age gap on a piece of paper. He only sees it as "passable" when he starts calculating the gap when she reaches her thirties.

  • In The Autobiography Of Malcolm X, Malcolm X cites the half-your-age-plus-seven rule as having factored into his decision to propose to his future wife.
  • One of the first recorded instances of the half-your-age-plus-seven rule is in French-born author and journalist Max O'Rell's 1901 advice book Her Royal Highness Woman. It may predate O'Rell, as he presents it not as his own invention but as a very good piece of advice that he "heard the other day." A reading of the original text reveals some of the Values Dissonance inherent in the idea that a man "should" be older:
    Never marry a woman richer than you, or one taller than you, or one older than you. Be always gently superior to your wife in fortune, in size, and in age, so that in every possible way she may appeal to you for help or protection, either through your purse, your strength, or your experience of life. Marry her at an age that will always enable you to play with her all the different characteristic parts of a husband, a chum, a lover, an adviser, a protector, and just a tiny suspicion of a father.
  • In the 1903 novel The Little Shepherd of Kingdom Come, Miss Jennie cites the half-your-age-plus-seven rule as a French saying, possibly referencing Max O'Rell.
  • Sense and Sensibility: Discussed a lot when Colonel Brandon falls in love with Marianne Dashwood. He is 35 and she is 17, and she thinks that he's old enough to be her father. Her sister Elinor thinks that it is a significant gap, but says a woman of 27 and a man of 35 might be quite happy together. Near the end of the novel, Colonel is still very much in love with her, and the narrator says he had "little to do but to calculate the disproportion between thirty-six and seventeen".
    Marianne: But thirty-five has nothing to do with matrimony.
    Elinor: Perhaps thirty-five and seventeen had better not have any thing to do with matrimony together. But if there should by any chance happen to be a woman who is single at seven and twenty, I should not think Colonel Brandon's being thirty-five any objection to his marrying HER.

     Live-Action TV 
  • In Friends, Joey apparently gets his algebra mixed up, making the age gap sounds even worse than it is:
    Joey: Yeah, come on, think about it. You're 18, okay, she's 44. When you're 36, she's gonna be 88.
    Frank: What, you don't think I know that?
    • In a later season Ross starts dating one of his college students. He acknowledges there's an age gap and it looks as if Joey's about to do the math for him again but this time he reaches a different conclusion.
      Ross: I know when I'm 90 she'll be like 80 and it won't seem like such a big difference.
      Joey: No, that's not what I was going to say at all. No, what I was going to say is when you're 90 you'll still have the memory of what it was like to be with a 20-year-old.
  • Mrs. America: Phyllis (b. 1924) and Fred (b. 1909), he even said that "it's biology" that men will get a younger wife after their first one and said that when he was getting active in far-right politics against FDR she was only "in saddle shoes".
  • In Parks and Recreation Andy (29) asks Tom how young is too young to date. Tom quotes the half-your-age-plus-seven rule, which, in Andy's case, would be 21 and a half, causing Andy some consternation when he realizes this technically puts the 21-year-old April in the "too young" range. He gets over it. It helps the audience that the age gap between the actors is only five years instead of eight (and that Andy's mental age at best is around 21).
    Andy: April's the best, but she's 20. When April was born, I was already in the third grade, which means if I were friends with her back then, I'd have been friends with a baby. I don't know anything about infant care... my god, I could have killed her!

  • Abbott and Costello had a routine where Costello claimed he was 25 and had fallen in love with a five-year-old. Abbott suggests if Costello waits five years, he'll be three times her age instead of five times. Abbott then suggests if Costello waits ten years more, he'll only be twice her age. Costello asks Abbott how long until he and she are the same age.
  • In The Moon is Blue, Patty is 21 years old and finds out from Don that he's 28 years old. (In the film version, she's 22 and he's 30.) She's quite delighted with her calculations:
    Patty: Isn't that amazing? It just works out.
    Don: What does?
    Patty: Haven't you ever heard that the girl is supposed to be half the man's age, plus seven?
    Don: What girl? What man?
    Patty: Never mind. Beat it.
  • In Princess Ida, Prince Hilarion reflects in a song that, at the time of his Arranged Marriage, he was twice Ida's age, and that "augurs ill for married life." Still, he was only two years old back then, and she has gained on him in the twenty years that have passed.

     Visual Novels 
  • In Hustle Cat, the Big Bad specifically references this trope if you're on Graves' route, as Graves is twenty years older than nineteen-year-old Avery.

  • xkcd #314 shows the "Standard Creepiness Rule" listed as "Don't date under (age/2 + 7)", providing a minimum age if not an ideal age.
  • In Yumi's Cells, Rational Cell and Emotional Cell have a laugh about 32-year-old Yumi being six years older than her crush, Wook. They remark that she was in university when he was in middle school, and there are a lot of younger women in the office that Wook could date over Yumi.

     Web Original 
  • In a Studio C James Bond sketch a.k.a. "Unfit for Espionage", Bond tells his female partner that she won't make it in the next movie because of her age (she's almost 30). Then he iterates the "rule of seven" to her like this...
    James Bond: You know the rule, half Bond's age minus 7. (Beat) ...divided by 2.
  • The May–December Romance trope on This Very Wiki specifies an age gap of at least thirty years before examples qualify.
  • In xkcd's spinoff What If?, a writer asks what would happen if each person had one soul-mate and could be happy with no one else. Randall ends up using an age limit much more strict than x/2 + 7, arguing it would be creepy if a couple met as children (30 & 40 isn't so bad, 5 & 15 is a problem).

     Western Animation 
  • In The Simpsons, Lisa falls in love with a cowboy who is 5 years older than her. When Marge says that he is too old for her, Lisa points out that the difference won't matter when they are both adults.


Video Example(s):


Jesse does the math

35-year old Jesse Fischer finds himself attracted to 19-year old Zibby but their 16-year age difference bothers him. He then starts calculating their would be ages and finds himself more comfortable with the idea.

How well does it match the trope?

5 (7 votes)

Example of:

Main / AgeGapAlgebra

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