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Butterfly Effect

Butterfly Effect


The Butterfly effect is an observation that in complex systems, small changes can result in large differences in outcomes. The term was coined in 1961 by Professor Edward Lorenz. He was one of the first meteorologists to use computer-based models to forecast the weather.

To save time when inputting data into the computer Lorenz reduced the number of decimal places from six to three. He was shocked to see the model’s prediction was radically different from what he had previously seen when had had used six decimal places. The butterfly effect is also a component of chaos theory where it is the sensitive dependent variable.

The butterfly effect can also be seen in A/B testing where small changes to the user experience and conversion rates can result in large differences in sales and revenues. Websites can of course be complex ecosystems with hundreds or thousands of interconnected pages and many potential customer journeys.

Image of A/B test on bwin.com casino homepage for balance deposit prompt

Source: Conversion-Uplift.co.uk 2016

For this A/B test on the casino homepage of bwin.com we triggered a deposit prompt pop-up every time a player’s balance fell below €6 or if they had a zero balance in their account. Displaying the deposit prompt resulted in a 5.8% uplift in users entering the cashier and a 6.2% uplift in revenues. As the change resulted in more frequent deposits from customers it increased total revenues by over €2m a year.


The butterfly effect is a powerful force for website optimisation. Little things matter, whether it is using their name to welcome a visitor, offering personalised recommendations or just making sure navigation labels are clear and unambiguous.

By getting those little details right you help establish credibility and trust with users. It helps make the customer experience more pleasurable. This ensures your customers can relax and means that they act more intuitively and make decisions faster than if they were feeling insecure or uncertain about your website.


Conversion marketing – Glossary of Conversion Marketing.

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A/B testing software – Which A/B testing tools should you choose?

Types of A/B tests – How to optimise your website’s performance using A/B testing.


Butterfly icons created by Freepik – Flaticon