NSW Demonstration — Codebook (Case C)

The National Supported Work (NSW) Demonstration was a randomized evaluation (mid-1970s) of a subsidized transitional-employment program for severely disadvantaged workers. These files are the widely used Dehejia–Wahba public extract (the “NSW-DW” sample with 1974 earnings), retrieved from Robert Dehejia’s data page (users.nber.org/~rdehejia/data). Public, free, no registration.

Files

| File | Rows | What it is | |—|—|—| | NSW_experimental.csv / .xlsx | 445 | The randomized sample: program (treat=1, n=185) vs. randomized control (treat=0, n=260). Use this for the true experimental effect. | | NSW_observational_cps.csv | 16,177 | The program group (treat=1, n=185) plus a non-experimental comparison group drawn from the Current Population Survey (treat=0). Use this to show how a naive observational comparison misleads. |

Variables

| Variable | Description | Units | |—|—|—| | treat | 1 = NSW program participant, 0 = comparison/control | indicator | | age | Age at enrollment | years | | educ | Years of schooling | years | | black | 1 = Black | indicator | | hispanic | 1 = Hispanic | indicator | | married | 1 = married | indicator | | nodegree | 1 = no high-school degree | indicator | | re74 | Real earnings, 1974 (pre-program) | $ | | re75 | Real earnings, 1975 (pre-program) | $ | | re78 | Real earnings, 1978 (post-program; the outcome) | $ |

The headline results (reproduce these in Excel)

• Experimental (NSW_experimental): treated 1978 earnings $6,349 vs. control $4,555 → effect = +$1,794.
• Observational (NSW_observational_cps): treated vs. the CPS comparison group → −$8,498 — the sign flips. This is the classic demonstration that selection bias defeats naive comparisons (LaLonde 1986; Dehejia & Wahba 1999).

Real, public-domain research data. Source: Dehejia & Wahba (1999, JASA); LaLonde (1986, AER).