Online shopping to a large extent defined holiday shopping this past season, with mobile commerce at the same time coming into its own. The down side to any kind of boom in e-commerce, though? An inevitable concurrent spike in virtual shopping cart abandonment.

The problem's not a small one. Some $4 trillion worth of merchandise was left hanging in virtual shopping carts last year, according to Business Insider Intelligence. 

So what’s happening? And what are some easy changes retailers and marketers can do to change it? 

Check-out

Some 91.5% of shoppers leave a retail site without even putting anything in their carts at all, according research by behavior analytics firm Bounce Exchange. Of those that “add to cart,” some 68.4% don’t complete their purchase—only 31.6% do, Bounce Exchange found. ​

While sales associates in physical stores can see toe-tapping impatience on the part of customers, and have an opportunity to open a new register (or swoop in with a payment-optimized tablet) to save the sale, that's not quite possible online. E-retail customers who get fed up with slow sites or too many e-hoops to jump through will simply leave the check-out process.

Even asking whether a customer is new to the site or returning can shift her focus from the items she wanted to trying to remember which email she may have used previously, greatly increasing the chance that she’ll quit the process altogether, according to KISSmetrics. 

And some 14% of checkouts are chucked when there’s no guest checkout, according to an infographic from SurePayroll. To avoid that, retailers should require only an email, not full registration, and offer a full range of payment options, says Ryan Urban, Bounce Exchange co-founder. 

“Not all shoppers will have their credit card handy so having the choice of Paypal, Apple Pay or other financing options will go a long way,” Urban says.

Curb the social media at checkout

Bounce Exchange has found that the value of social media to retailers may be overstated, and that, in any case, any kind of social media interactions or enticements should be left until after check-out to avoid ditched carts.

“Remove all extra navigation from the checkout process such as social media channels,” Urban says. “Don’t distract your shoppers from doing the one thing you want them to do—buy! Get the purchase done first, then ask them to endorse you later.”

And checkout must be just not smoother but also faster than it is now, especially on mobile, according to Urban: “At least three times faster than it is now. It will make the shopping experience more enjoyable.”

Rethink shipping and other surprise charges

More than half (56%) of those quitting before online checkout do so because of unexpected charges that make them think twice about their purchase, according to Shopify.

Shoppers want to see shipping times and charges clearly noted at checkout, and will wait longer in exchange for free shipping, according to a report by UPS and comScore. Nearly 60% (58%) of those ditching their online carts say they did so because shipping charges were too high, and 37% say it was because charges were noted too late in the process, according to the report.

Communication

But the UPS/comScore report also found that some 55% of those abandoning ship did so because they’re weren’t ready to make their purchase. They wanted to “wait till later,” according to the report, providing retailers with an opportunity to save the sale.

That makes it imperative for retailers to enable their sites to allow shopping carts to stay filled for when those customers return. Marketers can also send friendly emails reminding customers of what they have in their carts, which has proven to work.

In fact, almost half of such emails are opened and 13.3% are clicked through. More than a third of those lead to a sale, and the average order value of shopping carts recovered through email is 19% higher than other purchases, according to SaleCycle.

Handled right, full but abandoned shopping carts can be an opportunity, says Bounce Exchange’s Urban.

“After running multiple of tests across numerous e-commerce sites we’ve identified proven fixes to decrease site / cart abandonment and increase conversion,” he notes.