Everyone lies at one point or another — especially when they are asked to describe themselves. Marketers tend to rely on surface demographics such as age, gender and income, but unfortunately, people even fudge these for a multitude of reasons.

How can advertisers be assured that the data they’re receiving is accurate?

One way you can be more confident in the data is by looking at its origin. Some sources are simply better than others. Let’s take a look at a few that should be approached with some skepticism.

Dating sites

Many free dating sites make the bulk of their money selling user information to advertisers, ignoring the fact that a dating site is hardly the best environment to glean the truth. In fact, a University of Wisconsin study found that about 81% of people who are dating online are lying about at least one physical attribute — height, weight or age — all factors that an outside party could notice right away. If that many people are lying about something easily observed, how many are willing to lie about things that are not so obvious?

If you’re the one purchasing this data, be cautious — as if you were on a first date with a stranger.

Entrepreneurship-oriented Sites

Entrepreneurs have lofty ambitions, and generally fall somewhere between wildly optimistic and delusional.  Entrepreneurship-oriented sites are good places to spot “liars” online, especially when the truth is a barrier between an amazing idea and its next round of venture capital.

According to our research, even personal income data from self-styled entrepreneurs is significantly inflated. For example, users on venture capital sites are 8.55 times more likely to over-report their income, closely followed by funding sites (8.51x), franchise sites (7.73x), and startup content (7.42x).

Job and Career Websites

Another place where users tend to overstate their current or most recent salary is on job and career sites. Our research shows that income data from users on these sites is 6.28 times more likely to be inflated. This makes sense, as users here are likely presenting an ideal professional persona to make them more attractive to recruiters — and more worthy of a higher salary at their next gig. But this is not good news for advertisers who gather income data on these sites.

Loan Management Sites

On the other side of spectrum, there are places where people are actually underestimating their income: loan management sites. According to our data, people are 8.56 times more likely to underreport their income on student loan sites, and 9.75 times more on general debt sites. Debt can be such a heavy load that it skews perception about all financial matters.  So unfortunately, income data here is also misleading.

What’s the solution? Yes, people lie — but an understanding of the psychology of why is half the battle. If your customer feels burdened with debt, that’s now your reality. Advertisers need to meet claims about data with a wary eye. Approach your data with discretion instead of blind faith or wild assumptions. You may just have your most successful campaign yet.