Heterogeneous Impact Disparity

In Simple Words

Imagine giving free bus passes to two people: one who already owns a car and one who has no transportation at all. The car owner barely uses the bus pass and sees little change in daily life, while the person without a car uses it every day to get a job, experiencing a massive life improvement.

Research question

Standard evaluations often measure public works impacts using broad population averages, obscuring major differences in benefit distribution among participants. When programs recruit individuals with viable alternative income sources alongside the deeply unemployed, overall net impacts become severely diluted.

Participants

Low-income urban and rural youth participating in public works programs in Côte d'Ivoire.

Study Design

Randomized controlled trial measuring distribution of short-term income gains across participant impact quartiles.

Results

The upper quartile of participants who benefited most from the program saw short-term earnings increase by 2.2 times the earnings gain experienced by participants in the lowest quartile.

Takeaway

Screen applicant baseline employment levels prior to enrollment to select individuals with zero competing labor opportunities.

Read alongside the research

Plain-English glossary

Original explanations, informed by the references below. Examples are illustrations, not data from the studies above. The research text stays unchanged.

Baseline

The starting measurements in a study. Researchers use these to compare what participants were like at the start with what happens later.

ExampleBefore a training programme starts, researchers measure workers’ earnings. That first measurement is the baseline.

GET-IT glossary · Baseline characteristics ↗Read more about baseline →

Randomized controlled trial

A study that uses chance, like drawing lots, to decide who receives each option being compared. Researchers compare the groups’ outcomes to estimate the effect of those options.

ExampleA lottery assigns volunteers to a training programme or a comparison group. Researchers then compare their outcomes.

GET-IT glossary · Randomized study ↗Read more about randomized controlled trial →

Related findings

• Ability-Heterogeneous Wage Returns →Labour & employment

  Imagine a nightclub with a strict dress code based on exam scores where high scorers enter easily without extra effort. For high-scoring individuals, additional work experience adds little value because employers already hire them based on test scores.

• Employability-Driven Effect Heterogeneity →Labour & employment

  Think of an integration agreement like a mandatory study schedule given to students. High-performing students who would study effectively on their own derive no benefit and may feel needlessly restricted, whereas struggling students who lack momentum get the structure and external push needed to achieve results.

• Gender-Differentiated Employment Gains →Labour & employment

  Think of a community gym that only offers heavy weightlifting equipment, which mostly attracts young men. If the gym adds cardio machinery and offers specific time slots for women, a whole new group of people starts exercising, driving up the total overall attendance of the facility.

• General Equilibrium Wage Spillovers →Labour & employment

  Imagine a small town where a single large factory hires almost everyone at low wages because workers have no alternative options. If the government opens a massive construction project next door offering higher pay, the factory owner is forced to raise wages to prevent workers from quitting.