LESSON 8 OF 13
Why a 10% conversion rate lift is not a 10% profit lift
Testing one variable at a time, and the margin maths people skip.
Conversion rate is the percentage of visitors to your site who end up on the order confirmation page. Its relationship to revenue is linear: conversion rate goes up 10%, revenue goes up 10%.
Testing it properly
Improving conversion rate means testing copy, images, button colours, layout and page flow — and testing them one variable at a time. Change the headline and the button colour together and you cannot tell which one the customer responded to.
Volume decides how ambitious you can be. At 3,000 visitors a month you need to be careful about limiting variables. At 30,000 you can run multivariate testing, which any conversion rate optimisation platform will support. The traffic going through the test is what determines whether you ever reach statistical significance — without enough of it, a test takes forever to tell you anything.
The part that gets skipped
As conversion rate rises, so does revenue — and the costs attached to that revenue rise with it. Cost of goods, shipping, fulfilment and credit card fees all scale.
The distinction that matters
A 10% increase in conversion rate is not a 10% increase in contribution profit or net profit. It is a 10% increase in revenue, and you then have to apply your variable margin to that additional revenue to see what it actually contributed.
Not every metric behaves this way. Pricing does not: when you raise prices there is no real marginal cost on the additional revenue earned, unless you have to spend considerably more to acquire the customer at the higher price point. That asymmetry is why pricing sits above conversion rate in the list of levers.