Husbands and wives bickering over the breakfast table may find it hard to believe, but mounting evidence suggests that married couples are less likely to develop dementia or to get other serious conditions such as cancer and heart disease than their single counterparts [source: Parker-Pope]. Happily, marriage also seems to have a positive impact on auto insurance rates.

The fact is that married couples are less likely to get into car accidents. There are various theories about why this might be the case; some sources say that married drivers tend to drive less than their single counterparts. Other sources hypothesize that married drivers have more stable, and therefore less risky, lives than singles. Whatever the reason, statistics show that married drivers have fewer motor vehicle accidents and injuries than single people. In fact, one New Zealand study showed that never-married drivers had twice the risk as married drivers of getting injured in a car accident [source: Whitlock].

Getting married, therefore, generally has a positive effect on your car insurance rates. Most auto insurance carriers offer a discount to married drivers. Even men under 25, who generally get stuck with the highest auto insurance premiums, receive a discount for being married. Married same-sex couples (in states that recognize civil unions and domestic partnerships) also qualify for the benefit, at least from the two biggest U.S. auto insurers, State Farm and Allstate [source: Edgerton].

Though marriage is generally a slam dunk for reducing auto-insurance premiums, this doesn't mean that newlyweds should always combine their auto insurance. If both partners have good driving records, then combining insurance may help you save even more. Adding a spouse as a secondary driver and/or adding your spouse's vehicle can pave the way to even greater discounts, such as multi-policy and infrequent driver discounts. On the other hand, if one partner has a less-than-perfect driving record or if one of you receives a speeding ticket or a DUI or has an accident in the future, the entire policy could be negatively affected.

If marriage tends to have a positive effect on auto insurance premiums, is the inverse also true for divorce? Yep. In addition to losing any marriage discount that might be in effect, divorcing couples may also lose multi-car and other discounts. Changing residences or commute times may also negatively impact your auto insurance rates.

Access to cheaper auto insurance is hardly a reason for matrimony, but there are clear benefits when it comes to auto insurance rates.