2021 is going to be another glorious year for e-commerce.

It is that time of the year when most of us are looking back at the “total addressable market” estimates to plan for specific campaigns. Unlike us, if you had your 2021 kick off in Q3, bless your soul. You are an enlightened being.

For the rest of you, for whom e-commerce is a strategic market, I have a question — have you built your total addressable market (TAM) and serviceable addressable market (SAM) estimates for 2021 considering how things evolved in 2020?

It’s important to understand the underlying business model dynamics of companies and visualize TAM from those perspectives.

For most of us, research is a mind-numbing, repetitive exercise of clicking through links on Google until they all turn purple — at which point we start seeking the simplest possible explanation. For e-commerce, addressable market estimates come in the form of headlines from platforms like Shopify. The company quotes a merchant count number in its earnings calls and that becomes the basis for guesstimating the current TAM of e-commerce companies.

The other, rather simplistic approach is to look at the user-base count from several databases that publish tech platform-level user stats.

In reality, the simplest answer is not the right answer.

Let’s take e-commerce shopping cart installations. Shopify, Magento, WooCommerce, BigCommerce and others publish installation numbers that run into millions.

Here is the dichotomy that should frame your TAM discussions.

E-commerce is long-tail heavy. Yes, there are millions of merchants, but e-commerce revenue is a fat-tail phenomenon — meaning, a disproportionate amount of e-commerce revenue comes from a few tens of thousands of companies.

PipeCandy publishes bottom-up TAM estimates with detailed data cuts by technology, logistics and payment system adoptions by firms across revenue tiers across all major markets. One of the common misconceptions we see in how firms misinterpret TAM estimates is that they equate revenue to spend potential.