Sure, there's trust. But there's also the internet.
A new Pew Research study of the impact of the internet and cell phones on committed relationships reports that 67 percent of committed couples have shared a password with a partner or spouse.
Online calendars, social media profiles, even email addresses, not so much. But passwords, now that's true love.
"Password sharing does not vary by age, but it is more prevalent in higher-income households," according to the report, which is based on a survery of 2,252 adults aged 18 or older. Couples making more than $50,000 in a household are more likely to share passwords than those making under that amount.
Also, the longer couples have been together, the more likely it is that they share passwords. Couples who have been partnered for 6 years or more are more likely to have shared passwords than those who have been together less than 6 years (71 percent vs 59 percent).
Now, you know what to get your sweetie for Valentine's Day. It quick and cheap and must include at least one numeral and one capital letter.
Interestingly, in our digital age, the vast majority of couples told Pew the internet hasn't played a major role in their relationship at all — 72 percent of committed online adults said the internet has “no real impact at all” on their partnership.
Still, more and more say it has some impact than. The first time Pew asked that question in 2005, 16 percent of internet using couples said the internet had an impact. Today, that figure is up to 27.
And while most of those who admit to the internet having some impact on their relationship say that impact is positive, the percentage of those who say the impact has been negative is also on the rise. Negative impact could include an argument over how much time one partner spends online, or a partner being distracted by technology in some fashion.
Other salient findings in the report include:
* Sexting is up, thank you Anthony Weiner. Nine percent of adult cell owners have sent a sext of themselves to someone else — up from 6 percent in 2012. You don't even have to be in a couple to sext. You can just sext.
* 9 percent have resolved an argument with their partner online or by text message that they were having difficulty resolving in person.
* Only your parents share an email address. OK, so it's not just your parents.