5 Customer Engagement Metrics All Ecommerce Sellers Must Track Use available tools to determine best practice.

According to latest UNCTAD estimates, the global ecommerce market is worth $22.1 trillion, and it's only getting bigger. By 2019, approximately 80 percent of internet users will make at least one purchase online during the year.

Ecommerce represents a great opportunity to boost your sales revenue and connect with new buyers. However, there are numerous challenges that need to be addressed if you want to be successful in the ecommerce marketplace.

Related: 10 Reasons Ecommerce Sites Fail

Driving the right type of buyers to your site and getting them to consistently convert at a profit is a complex process. You'll increase your chances of success if you meticulously track your customer metrics and continuously make improvements according to the data.

Here are the five most important customer engagement metrics you should track if you want to prosper with ecommerce.

1. Cost per acquisition.

When using pay-per-click (PPC) advertising to drive traffic to your ecommerce site, it's important that you don't destroy your profit margins.

After you subtract your manufacturing and shipping costs from the retail price of your product, you will be left with a figure that indicates pure profit. As long as your cost per acquisition (CPA) -- the money it costs to acquire one new customer -- is less than this number, you're running ads at a profit and can think about scaling your campaign. Fortunately, you're not going to go bankrupt if a $5 per day Facebook ad campaign doesn't convert at a profit. Start all of your campaigns at a low ad spend, delete the losers, and scale the the winners.

You can lower your CPA by implementing the following steps:

• Split test all campaigns
• Exclude unprofitable regions
• Refine your targeting
• Maximize on-site conversions

2. Conversion rate.

It's critical that you track your conversion rate -- the percentage of people who arrive on your site who go on to become paying customers.

If you're able to drive a lot of traffic to your website, but very few visitors convert, that's not good. It can be far more profitable to drive a smaller amount of traffic to your site and ensure each visitor is an ideal match for your product so that your conversion rate is high.

With Facebook ads, you can exclude certain age groups (e.g. younger people don't tend to convert well for high ticket items), focus on specific regions, and select key interests to ensure you're targeting people who are fanatical about your niche, rather than people who are lukewarm.

If your targeting is already good, but you want to improve on-site conversions, try tweaking these landing page features:

• Social proof and credibility elements, such as reviews and trust symbols
• Your "Add to Cart" button color and placement
• Product photography
• Scarcity elements, like countdown timers
• Pricing
• Payment options -- the more you have, the better

3. Average order value.

While conversion rate optimization is one way to improve your store's profitability, getting each customer to spend more money at your store is another. Your average order value (AOV) represents the average amount that each customer spends with you. If you can increase this figure, then your CPA doesn't need to be as low for your store to be profitable.

If your Facebook ad campaign is teetering between mildly profitable and making a small loss, improving your AOV will allow you to scale your campaign.

Improve your AOV with the following actions:

• Add more products to your store
• Promote cross-sells and upsells
• Create bundle discounts

Related: Here's How to Master Facebook Advertising and Why You Must

4. Customer lifetime value.

Some marketers have a bad habit of focusing all of their efforts on bringing in new customers, while completely neglecting existing customers. A great way to increase the profitability of your store is by improving your customer lifetime value (CLV) -- the average amount a customer spends during their relationship with your brand.

If you know how much a customer is worth to you long-term, you can plan for longevity and scale your business more effectively. If you're able to get repeat customers and your CLV is high, you can get away with having a higher CPA to get each customer in the door initially.

Some ecommerce businesses make no profits on first time customers; their models are based on repeat business.

Improve your customer lifetime value with the following actions:

• Promote loyalty programs
• Engage your customers with email and content marketing
• Run competitions to build rapport with customers
• Improve your AOV
• Use social media as a customer services channel
• Feature brand advocates on Instagram
• Offer discounts in exchange for video reviews

5. Cart abandonment rate.

In a study by Adobe on consumer spending, it was found that 30 percent of carts result in an order on desktop devices, whereas only 19 percent of carts result in an order on mobile devices. This means that 70-81 percent of people filling up their ecommerce shopping carts are abandoning them and leaving the site without making a purchase.

If your cart abandonment rate is 70 percent or higher, this represents an enormous opportunity for reconnecting with people who showed an initial interest in your product, but who didn't convert. You can revive abandoned carts with the following tactics:

• Create an email sequence for abandoned carts
• Retarget those who abandoned their carts using Facebook ads
• Add multiple payment options to your checkout to increase conversions
• Implement a checkout page progress indicator
• Allow guests to checkout without registering an account
• Prevent unexpected shipping costs from appearing at your checkout

Related: Troubleshooting Your Ecommerce Store: What to Do When No One's Buying

Finding the data required to track these metrics can be tricky. Your shopping cart -- like Shopify, BigCommerce or Magento -- may provide some insight, while other information can be found from your web host's analytics system. Bluehost, Hostgator and iPage are common options.

Use the tools at your disposal to track these important metrics, and you'll be well on your way to ecommerce success.