Thanks for reading!

Here is a link to the working paper:
www.iza.org/publications...

(Frequently asked QA2)

Does longer hours boost skills through learning-by-doing?

No, our data on manufacturing and sales output per hour do not support that.

(Frequently asked QA1)

Do (Japanese) women quit after birth?

No, in our firm, mothers don’t quit more than others. Instead, most opt for “reduced hours for parenting,” common in large firms.

Labor supply adjusts at the intensive, not extensive, margin.

6. What needs to happen?

Stop rewarding long hours in evals and promotions— work reorganization is key.

This levels the playing field for workers with diff time costs, promoting untapped talent and addressing the child penalty and talent allocation.

Equality and efficiency can go hand in hand 🤝

5. Implications to employers?

The current reward system traps “talented workers with high time costs” (often mothers) at the bottom ("untapped talent"),

while “lower time-cost workers who compensate with long hours” rise to the top

— leading to talent misallocation.

4. Our data do not support alternative hypotheses, such as:

❌ women’s career aspiration change following childbirth

❌ women with children are evaluated lower than observably similar men (incld. working hours) due to discrimination/implicit biases

3. Mechanism for missed promotions? — Past working hours matter

Our data support:

✔️ Long hours are rewarded with higher evaluation scores, boosting promotion prospects.

✔️ Mothers reduce hours post-birth, facing unequal promotion chances.

Time off for childbirth has lingering career effects.

2. Child penalty — key findings

▫️ 55% (46% mom penalty + dad premium)

▫️ Early on, time-based pay drives the penalty but fades over time.

▫️ By year 15, job-rank-based pay dominates, indicating missed promotions due to childbirth.

1. Study design

1️⃣ Estimate the child penalty by pay item using macthed-control event study

2️⃣ Examine the evaluation and promotion dynamics driving the penalty

3️⃣ Build a model of internal promotion aligning our empirical findings

5./ We show how MMWI can be used to evaluate public policies—and we see many more potential applications.

Since children's expenses are a key shared good, this framework also helps link women's changing economic roles to resource allocation for children.

4./ In Japan, welfare inequality has declined across birth cohorts, mainly due to lower intrahousehold inequality — a sign of women's improving economic position.

MMWI makes this trend visible.

3./ Those with less bargaining power benefit more from shared goods, which help redistribute welfare.

As a result, MMWI-based intrahousehold inequality is lower than when measured by private consumption alone— crucial for policies like fair compensation in divorce settlements.

2./ MMWI builds on the collective household framework, a key tool for uncovering "hidden" inequality within households.

In short, it factors in shared consumption (e.g., child investment, housing) while accounting for heterogeneous preferences and bargaining power.

1./ A large share of household resources is "shared" (see Japan's case in the figure).

How should we account for this when measuring intrahousehold welfare inequality?

We tackle this by proposing a Money Metric Welfare Index (MMWI), examining its anatomy, and applying it to Japanese data.

What's new?

We now provide a thorough comparison of MMWI with other intrahousehold inequality measures—both unitary and collective models.

We’ve also added more empirical results and explored new applications.

So, here is a short thread 🧵

I am also looking forward to it :)