In 2014, researchers asked men to estimate the size of the average erect penis. Their guess? 6.2 inches (15.8 centimeters). That's actually in line with what numerous scientific studies have reported. But guess what? Those studies are wrong.

Clemson University Professor Bruce M. King, senior author of the textbook Human Sexuality Today, drew attention to this issue in a recent review published to the Journal of Sex and Marital Therapy.

For years, researchers asked men to self-report the length of their erect penises by measuring along the top from the abdomen to the tip, and over that time, men consistently informed researchers that their members ranged from roughly 6.1 to 6.5 inches.

Can you see the problem with this procedure? Asking men to accurately report the size of their penises is like trying to eclipse the speed of light in a junker car: it's not gonna happen.

Whether because of measurement error, respondent selection bias (only men with larger penises want to participate in research), or good old fashioned misreporting (i.e. lying), it seems that studies employing self-report to find the length of the average erect penis have given us the wrong answer for decades.

When researchers actually measured erect penises in the lab from representative samples of men, the average length ranged between 5.1 and 5.5 inches. Globally, the real average is probably closer to the bottom of the range.

So the average erect penis is about an inch shorter than what most men think it is. The problem with this disconnect between perception and reality is that it has prompted male dissatisfaction with their genitalia. Surveys suggest that between 45 and 68 percent of men wish they had a larger penis. Forward-thinking male sexual health expert Dr. Bernie Zilbergeld once remarked, "It is not much of an exaggeration to say that penises in [men’s] fantasyland come in only three sizes—large, gigantic, and so big you can barely get them through the doorway."

These fantasies have fueled a booming and almost entirely BS industry of penis enlargement, replete with supplements, surgeries, and strange gadgets. One study found that heterosexual men's ideal penis length is about 7.3 inches. That's almost 40 percent larger than average and well beyond the size that heterosexual women in another study said they preferred.

According to King, members of the media, sex educators, and most of all, researchers, should strive to dispel unhealthy myths about penis size.

"Many of the anxieties men have about the size of their penis could possibly be alleviated if researchers and others would stop quoting average penis lengths based on studies that relied onself-reported measurements," he wrote.