The massive income/wealth gap of married vs non-married

[KMMK]

Like almost everything, the answer is "it depends". I spend more money when married or equivalent, as my personal housing and entertainment tastes are cheaper than the average person. And there is more to do when part of a couple, so I spend more money. My partner spends less money now that he's with me, as he's thinking more long-term and buys less toys to combat sadness/loneliness than he did before.

It's really about double-income, and some expenses being cheaper for two people together - housing, etc. But if someone is really spendy or someone doesn't work for money then those don't really lead to a better financial situation.

[Hotstreak]

Here are the financial benefits to being married, as I see them, as a single person:

Co-habitation (compared to living with a non-romantic roommate)
-  Does not require an additional bedroom, so rent or purchase price is lower
-  Less vacancy, since spouses move out less often than roommates
-  Ability to sign up for family plans or discounts on many services.. gym memberships, phones, health insurance, auto/home insurance
-  More likely to share cooking, care for you when sick, etc., allowing for bulk purchases & reducing incidental convenience purchases

Tax benefits (potentially)
-  Most people don't stay DINK's forever.. once those kids come things chance, especially if one partner reduces their work at the same time
-  For the FIRE crowd, it's much easier to live on tax free LTCG's and QD's in the married brackets, due to fixed costs like housing taking up a smaller portion of the overall "free" tax bracket.

Financial support
-  If one partner looses their job, they don't need to spend down savings the way a single person would.  Instead, they can rely on their partner's income (and tighten the budget up a bit) while they find new work.
-  Diversified income stream also allows greater risk taking - a married can take a higher paying job they have a chance of failing at, because they know their spouses income can cover if needed.  A single person has greater downside risk of taking the same job.  This is basically the same thing as the 1st point.

Retirement/Legal
-  Social Security and Pension benefits allotted to spouses, such as survivorship
-  Marriage is essentially a low cost contract that does not require renewal, and covers a large number of basic legal issues like medical control, transfer of assets upon death, etc., which a non-married person would need to hire a lawyer for, and may need to renew on a regular basis.

The beneficial behavioral changes being discussed are very interesting to me (and obviously don't apply to all couples).  I also wonder if there's a generational component.  If the parents model healthy long term relationships then their children are more likely to have the same, and IF there IS a financial benefit to being married, then those parents will pass the financial benefit to their children by paying for college, inheritance, etc.  That would show a correlation between marriage and wealth, but not causation, since the act of marriage is largely incidental compared to the benefits of a long term relationship.