You may think you communicate well, but the data says you probably don't.

Couples argue about money and finances more than just about anything else. The irony? According to a recent survey conducted by investment firm Fidelity, most couples -- 72% according to that survey -- say they communicate well with their spouses about finances. 

Unfortunately, the details of the survey indicate that's probably not the case for a lot of couples. Keep reading for a look at some of the data points that really stand out, and about things couples should be aware of when it comes to their financial situations, their spouses, and their futures. 

How much does your spouse make? That's just one of many things couples get wrong
This one has made a lot of headlines this year, and deservedly so. According to the Fidelity survey, 43% of those surveyed answered incorrectly when asked their spouse's salary range. Frankly, it's hard to fathom that nearly half of those surveyed didn't know, within a few thousand dollars either way, how much their spouse made. Apparently, one in 10 couldn't guess within $25,000 how much his or her spouse made.

One in three people also didn't agree on an expected lifestyle in retirement, and more than 60% didn't know or disagreed with a spouse on what their Social Security benefits would be in retirement. Maybe most disturbing was that 36% of couples surveyed didn't know how much investable assets they had. 

In other words, most couples like to think they communicate about retirement and finances, but the data shows that's just not the case. 

What are the potential repercussions? 
The first risk of this kind of reality versus a perception of good communication is the effect of stress on the relationship. There's a lot of evidence that stress is compounded by uncertainty, and a lack of knowledge about your financial situation is exactly the kind of thing that can compound that worry. This is one of the things at the heart of why couples tend to argue about money. 

Put another way, it's too important a thing to ignore.

According to the same Fidelity study, couples who had a solid financial plan in place tended to worry less about money and retirement, and to feel completely confident in their abilities -- as well as their partners' abilities -- to assume full financial responsibility, if needed. 

Simply put, the data strongly showed that those with a plan were more confident, less stressed, and more involved in both daily and long-term financial matters. 

Sound familiar? An involved partner is a happier partner 
One interesting data point really stood out in the survey: In relationships where one partner handled the majority of major financial decisions, that partner said that his or her spouse didn't want to be more involved the "vast majority" of the time. However, the answers their spouses gave in the survey painted a different picture, with more than one-third of spouses disagreeing, answering that they want to play a larger role. 

So it gets back to a lack of basic communication. 

Putting it all together 
Sure, a lot of people don't want to deal with all of the financial matters, and that's fine. However, it's probably not a good idea to just operate under the assumption that your spouse is one of those people who doesn't. 

Besides, even if you or your spouse isn't interested in getting deeply involved in the planning details, each person should know some basics, such as where to locate plan statements, important contact information, and how to access funds in case of an illness, injury, or even death.

After all, the worst-case scenario isn't making it into retirement a little short, but something bad happening to the spouse who handles everything, leaving the other partner to pick up the pieces, and not knowing where to start.

Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.