Kristen Mirenda
UX Writing + Design Thinking + Product Know-How
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Conversion rate optimization

Creating Hotwire's first UX A/B testing program and making millions with microcopy


In 2011, I was Hotwire's Lead Product Manager for hotel booking. I reserved 15% of the Scrum team's bandwidth for UX optimization experiments. I was the first PM at Hotwire to do this methodically on a live product.

I worked with the interaction designer to compile a backlog of ideas, starting with classic techniques like social proof. 

My strategy was to run as many tests as possible. I did this by prioritizing simple microcopy changes. I believed that success wouldn't correlate with scope.

We used a homegrown A/B testing system to measure the impact on booking rates. I could translate that into contribution margin (CM), or revenue minus costs. CM was Hotwire's key metric.

Here are a few examples of these experiments:

Hotwire hotel search results in 2011

Hotwire hotel search results in 2011

Confidence building

Hotwire uses opaque pricing. Customers don't know the hotel name until they make a non-refundable booking. In exchange, they get a deep discount.

Qualitative research confirmed this was too risky for a lot of people. So we added a tooltip showing a list of hotels they might get. 

It was enough reassurance for many users. The ones who saw the new microcopy booked at a higher rate, worth $1.4 million per year in additional CM.

Conversion rate optimization

Social proof

What else helps people take an action when they're unsure? Knowing that other people have already done it. We added a daily count of bookings for each result. It was worth $1.5 million per year in CM.

Conversion rate optimization

Strikethrough pricing

On Hotwire, there's not a single full-price rate corresponding to the discounted one. We calculated a representative rate and showed it as a strikethrough price. 

I worked with Legal to make sure our approach was okay and that the explanatory footnote was clear.

Now customers could see what a great bargain they'd be getting. The booking rate increased more than 5%. That was worth over $6 million incremental CM per year. 

After 8+ years, my microcopy is still in the UI. During that time, it would have earned Hotwire at least $50 million (and counting).


In the first year of the program, we completed ten A/B tests. Six of them showed a statistically significant increase in bookings. They added up to $15 million CM per year, far beyond expectations.

I had demonstrated the value of simple optimizations. As a result, Hotwire spun up a new team to focus on them full time.

tests in the first year
$15 million
yearly benefit