How to choose a north star metric: a case with data

Maya

Next week the board sets goals for July to December. The CEO wants MAU as the company goal: “it grew 58% since January”. Theo wants sign-ups. I need a recommendation, with numbers.

Alex Tutor

Then let's put the candidates side by side. Here are six months of monthly numbers. weekly_active_groups is the average per week in that month: groups where at least two members added or settled an expense.

Alex Tutor

Dataset · 6 rows

Halves monthly metrics, January–June 2026

Staff accounts excluded. Paid social campaigns started in April.

Download CSV

Columns
month: Calendar month
new_signups: New accounts created
mau: Distinct users who opened the app in the month
app_opens: Total `app_opened` events
expenses_by_people: Expenses added by people (recurring bills excluded)
weekly_active_groups: Average per week: groups with at least two members who added or settled an expense
plus_subscribers: Paying Halves Plus subscribers at the end of the month

Data

month	new_signups	mau	app_opens	expenses_by_people	weekly_active_groups	plus_subscribers
2026-01	3100	9800	61000	41200	1480	410
2026-02	2900	10100	62500	42300	1520	432
2026-03	3300	10600	66000	44100	1575	455
2026-04	5200	12400	74800	45000	1590	470
2026-05	6100	14100	83900	45900	1600	481

Show 1 more row

2026-06

6800

15500

90200

47300

1655

498

You

I'll start with the CEO's number. Growth from January to June is June divided by January, minus one.

Alex Tutor

Check it rather than trusting the slide.

Maya

Please do. If the board catches one wrong number, nobody listens to the rest of the deck.

Alex Tutor

Question 1

By how much did MAU grow from January to June 2026, in %? One decimal.

Your answer

Units: % (e.g. 12.3)

Alex Tutor

The CEO is right about MAU. Now the whole row: sign-ups +119%, MAU +58%, app opens +48%. Those are reach. On the value side, expenses added by people grew 14.8%.

Theo

And weekly active groups? That's the one Alex keeps pushing.

Alex Tutor

Compute it the same way. Then we'll put the two growth rates next to each other.

Alex Tutor

Question 2

By how much did weekly active groups grow from January to June, in %? One decimal.

Your answer

Units: % (e.g. 12.3)

You

So MAU grew about five times faster than the groups that actually share costs.

Alex Tutor

Put them in one ratio: weekly active groups per 1,000 MAU. January: 1,480 ÷ 9,800 × 1,000 = 151. June: 107. For every thousand monthly users, fewer groups are sharing costs.

Theo

My campaigns added 5,700 monthly users since January. That's not nothing.

Alex Tutor

It isn't, and it's real reach. Over the same months, weekly active groups grew by 175. The question is why so few of those users ended up in working groups.

Maya

Let's be careful before blaming anyone. Theo's campaigns have brought us great users before.

Alex Tutor

Question 3

Weekly active groups per 1,000 MAU fell from 151 in January to 107 in June, while paid campaigns ran from April. What is the best first hypothesis to check?

Choose one answerThe product got worse for existing groups, so they stopped sharing costsTracking of expense_added broke in AprilSummer trips pulled users away from their flatsMany new users from the campaigns open the app but rarely end up in a group with a second active member

Alex Tutor

Now run every candidate through the same tests: does it reflect the value users get? Does it lead revenue? Can teams move it through inputs? Is it hard to push up without helping anyone?

Maya

Plus subscribers grew 21.5%. That's between MAU and groups. Doesn't that make it a fair compromise?

Alex Tutor

Plus follows active groups with a delay: people pay for receipt scanning when they share lots of costs. It's the right number to check monthly, next to the north star. Steering by it invites paywalls in the way of sharing.

You

So every candidate is useful for something. The question is which one the company steers by.

Alex Tutor

Question 4

Match each rejected candidate to its main weakness as the Halves north star.

Pick an answer for each row. Choosing an answer that is already used moves it to this row.

MAU
Choose an answer
New sign-ups
Choose an answer
App opens
Choose an answer
Plus subscribers
Choose an answer

Maya

The CEO will say: “Groups grew 12%, MAU grew 58%. Why pick the goal that looks worse?”

Alex Tutor

Because it's the one that can't be bought. A MAU goal can be hit by doubling the ad budget while groups stall. Weekly active groups only rise when people actually split costs together.

You

And MAU doesn't disappear. It stays on the dashboard as a volume metric, next to the north star.

Maya

Give me the short version I can say out loud when the CEO pushes back.

Alex Tutor

Question 5Short answer · AI-checked task

The CEO says: “MAU grew 58% since January. Let's make it the company goal.” Reply in 3–4 sentences with numbers from the table.

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Maya

Now the one-pager I'll bring to the board: which north star, how it's defined, what feeds it, what we watch next to it and the numbers that make the case.

Alex Tutor

And one honest line about what the table can't tell us. These are monthly totals, so they don't show which users came from the campaigns.

You

Got it: a pick, a definition, a small tree, a guardrail, the numbers and one limit.

Alex Tutor

Question 6Case · AI-checked task

Write Maya's one-page north star recommendation for the board.

The Halves board sets the company goal for July–December next week. The CEO proposes MAU, Theo proposes new sign-ups. Maya asks you for a recommendation she can defend in the room, using the monthly table above (January–June 2026; paid social campaigns started in April).

Write 200–350 words:

Your north star, with a full definition (qualifying action, unit, exclusions, window).
Why it beats MAU and sign-ups, with at least three numbers from the table.
A small metric tree: two or three input metrics that feed it, each with the team that owns it.
What you keep next to it as context or guardrails.
One thing this table can't tell you, and how you would check it.

Dataset for this task: Halves monthly metrics, January–June 2026

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Alex Tutor

The board still gets MAU. It just stops being the goal the whole company steers by.

Alex Tutor

That’s the lesson. You answered every task — nicely done.

Next lesson: Funnels: order, window and who counts