Women's sizing is more disparate than ever before, studies show

If you've shopped online for clothes only to discover they don't fit, it's probably not you. More than likely it's because clothing sizes have become increasingly difficult to scale.

Size and fit were the top reasons why people return online orders, according to an analysis from post-purchase analysis company Navar. Their "The State of Online Returns: A Global Study" found that nearly 50% of shoppers buy multiple sizes with intentions of having to return some of them.

"Women are constantly bouncing between sizes or struggling to find the perfect fit," Ronen Luzon, CEO and founder of MySize, an online resource that helps shoppers find their appropriate apparel sizing based on real-time body measurements, told "Good Morning America." "Size variance is a real issue -- you can jump four sizes or so in jeans depending on what brand you're trying on."

How did we get here?

While sizing standards for clothing exist, as outlined by the American Society for Testing and Materials, manufacturers and ready-to-wear retailers are not legally required to adhere to them.

"Each manufacturer or design firm can imagine their ideal person, whether this person be curvy, straight or busty, and make clothing to fit this particular body shape," Dr. Lynn Boorady, professor and department head, Design, Housing and Merchandising at Oklahoma State University, told "GMA."

The average body shape in America has also changed over the years.

In 2002, Size USA conducted a national study on the body scans of more than 10,000 people to reflect an updated general sizing scale, according to an article on Buffalo State University's Fashion and Textile Technology website. The study found that the rectangular-shaped body is more prominent in the United States than the formerly standard hourglass.

"Humans are not all the same shape and we have been changing shapes -- we change shapes when we age, we change shapes when we gain or lose weight … Some people gain weight in the waist, women in the bust area and some in the hips as well as thighs. This makes it more difficult to fit clothing, particularly garment sizes that are developed on the basis that the population has an hourglass shape," Boorady said. "One of the issues we see in the past 20-30 years until now includes increasing numbers of the population that are overweight and obese."

Boorady also points out that with the diverse nature of America, made of people of different ethnic backgrounds, ages and cultures, there is now a greater range of body shapes to fit and different cultural attitudes around fit.

"On top of that, people have personal preferences to the fit of their clothing," she adds. "The style of their clothing and the comfort as well as feel."

Now, to combat the apparent sizing disparities faced, platforms such as MySize give shoppers the option to use mobile body scans to find exact real-time measurements within seconds.

"In a sense, we provide the solution to making sure brands are both inclusive of all sizes and easily accessible to customers," Luzon said.

Another platform, True Fit, has similar functionality in helping people find their true size. The company uses user data to decode personal style, fit and size, as well as buying behaviors of consumers.

True Fit also offers a mobile App integration which allows anyone to use a scanning functionality that works with a wide variety of retailers to find the best size recommendations.

Clothing size disparities also affect people who don't fit into outdated scales of straight sizes that traditionally stop at size 12.

"Very few designers have the plus-size woman as their ideal," said Boorady in a statement. "That is slowly changing as more niche markets emerge with clothing designed for large-busted women, tall women, and plus sizes."

Emerging e-commerce brands such as 11 Honoré have made a mission to open up more options for women above a size 12 by specifically carrying the exclusive designer and contemporary collections ranging from sizes 12-24.

Katie Murphy, VP of client services at 11 Honoré, told "GMA," "The biggest concern I see with the women I interact with every day is they really have no idea what size they are. Some know their measurements, which is super helpful, but accurately applying those measurements across multiple brands is usually very inconsistent."

She continued, "I probably say 25 times a day to people that most women are very likely three sizes from brand to brand. The inconsistency, combined with the lack of options is the biggest source of concern and honestly, what makes women hesitant to shop online."

"We, along with the designers and brands we carry, have shown that it is possible to extend sizing if one wants to do it," adds Patrick Herning, founder, and CEO of 11 Honoré. "We support our designers to properly grade their collections beyond a size 10 so that the integrity of the garment is intact."

There are also retailers such as Universal Standard that carry sizes 00-40 that go the extra mile to not only provide options for a massive amount of body types, but the brand also understands how often sizing can change. The brand's Fit Liberty shopping program allows shoppers to return items and replace them with new size completely free of charge.

One of the most recent studies completed, Size North America, was conducted by Human Solutions of North America, which surveyed 17,820 men, women and children through the use of 3D body scanners.

"Size and fit are key factors in the buying process of fashion and apparel’s customer, and so are comfort and safety for a customer of the automotive industry," Human Solutions of North America describes on their website as one of the reasons behind the study. "Using the survey data in your product design will be a huge market benefit."