[mention eng constraints: weren’t able to iterate after launch…]

How balance works and why it’s important for the ecosystem

Mercari works like this: when a user made a sell on Mercari, the earnings becomes their ‘balance’ on the platform. The user can then use that balance to purchase more items… or transfer out to their bank.

From a business perspective, here are some benefits to keep balance within Mercari:

1. Reduce transaction fees

   • Mercari absorbs the transaction fee when user withdraws. Increase balance = better financial shape for Mercari

2. Increase user engagement

   • Keeping balance within the ecosystem encourages users to use the platform more frequently.

   • User can apply balance to purchase more items, or increase their sells to accumulate more balance.

Identify areas to surface balance, with buy intention in mind

From the very beginning working on this project, I was aware that when users withdraw balance from Mercari to their bank account, Mercari absorbs the transaction fee. If we highlighted balance where users have a weaker buy intent, it might trigger more balance transfers = more money lost on Mercari. Because of that, finding the right balance to surface information became the crucial first step (pun intended).

To better identify potential surfacing areas, I mapped out a flow that focuses on buy intention.

By mapping out the flow chart, opportunity areas to surface balance became apparent:

• ❌ Home tab isn’t the most ideal place to surface because the buy intent at that step is relatively low, hence users are more likely to withdraw

• ✅ Item detail page is the most ideal area to surface because it provides the most item information and is oftentimes the step user makes informed purchasing decision

The key: lower the cognitive load

While getting inspirations from other apps, one key realization I had was the importance of low cognitive load for pricing. The beauty of other successful apps, they’ve managed to provide very simple interaction.

• Don’t let users calculate

• Straightforward interaction and text

Explorations

After some sketching, I ended up settling on two methods to present balance information. A static component that directly lists out final price a user would pay using balance (and coupon if applicable), an expandable component that provides breakdown of discount items used upon clicking.

[section add competitive analysis]

A/B test result

With the two designs, we quickly launched an A/B testing to all users with balance. 50% of users carrying balance will see V1, and the rest will see V2. Partnered with a business analyst, PM and I closely monitored the data for one week. The result: expandable component (V2) yielded higher balance usage rate by 12%.

The data suggested having the breakdown of balance and subtotal was especially useful, urging users to use their balance more.

[what’s different between v1 and v2?]

Design for importance

And we hide the rest.
Expandable component enables sharing only necessary information upfront. While clicking, users can still access the breakdown of their discounts.

Design for transparency

When it comes to pricing, users care about transparency just as much as the final price. When the component is open, it shows all the breakdown for users. On Mercari, there are several price reduction mechanisms: balance, coupon, and credits. By being transparent of what method is taken into calculation, it helps user set better pricing expectation before checkout.

Scenario mapping

Partnering with a content designer, we mapped out copy variants for different scenarios. This was especially helpful for engineers to work on surfacing balance copy and logic.

Design for clear pricing

Previously, the price information on the item detail page was messy, contributing to more cognitive load. Part of the project effort was to clean that up.

• Aligned visual and content between app and web

• Consolidated similar content and removed the noise