Mobilize through people
Community engagement
Community-engagement interventions work through existing trusted relationships — community health workers, peer educators, neighborhood associations, faith communities. The mechanism is trust: messengers matter as much as messages, and a familiar face changes how the same information is received.
12
Experiments
8
Policy areas
1989–2021
Year span
8 / 12
Positive
When it works
When the target behavior depends on trust (vaccination, contraception, treatment adherence) and when the existing institutional intermediaries lack credibility with the population. Effects are often larger than top-down communication campaigns at comparable cost.
Watch out for
Quality and consistency of community workers is hard to maintain at scale. The trust that makes the mechanism work cannot itself be rapidly manufactured; programs that import 'community engagement' as a tactic without the underlying relationships often underperform.
Community engagement across policy areas
Public Safety· 4 experiments
- Mixed
Cure Violence — Chicago
University of Illinois at Chicago / Chicago Department of Public Health · Chicago, USA · 2000
Effect: Shooting reductions of 16–28% in treated communities; statistically significant in 4 of 7 sites; homicide trends improved relative to controls
- Mixed
Cure Violence / Group Violence Intervention — Community Violence Interruption
University of Illinois Chicago / National Network for Safe Communities (John Jay) · Multiple US cities · 2000
Effect: Cure Violence: Baltimore evaluation found homicides fell 34% and nonfatal shootings fell 21% in program sites vs. comparison areas; NYC results mixed (some sites positive, others null); New Orleans: 49% reduction in homicides in program areas. GVI: National multi-city evaluation (2019) found cities implementing GVI had 17% lower gun homicides than comparable non-GVI cities. Both programs show heterogeneous effects across sites.
- Positive
Drug Courts — Randomized Trial Evidence Base
National Institute of Justice / RAND Corporation / multiple jurisdictions · Multiple US cities · 1997
Effect: Recidivism: −8 to −14 pp vs. standard prosecution in RCTs; drug use: significant reduction while in program, mixed evidence of persistence; incarceration days: substantially fewer during supervision period; cost savings: $3,000–$13,000 per participant vs. incarceration
- Positive
Boston Ceasefire — Group Violence Intervention
Boston Police Department / Harvard Kennedy School · Boston, MA, USA · 1996
Effect: Youth homicides: −63% in 24 months (from 3.8 to 1.4 per 100,000); gun assault incidents: −25%; effect attributable to intervention not broader national trend through synthetic control analysis
Parks & Public Space· 2 experiments
- Positive
Urban Tree Canopy and Heat Equity
American Forests / multiple city partners · United States (30 cities) · 2021
Effect: Canopy increase of 8–15% in 5 years; land surface temperature reduced 2–4°F in treated blocks; survival rate 68%
- Positive
Community Park Advisory Boards
City of Los Angeles / UCLA · Los Angeles, USA · 2014
Effect: Parks with PABs showed significant increases in physical activity intensity and individual park use vs. control