Medium and Message by Mail: A Field Experiment to Promote Low-Income Assistance Programs

Limited awareness impedes take-up in low-income utility assistance programs, which often suffer from low uptake. This study uses a field experiment to evaluate direct mail as a means of reducing learning burdens and thereby increasing participation in financial assistance programs offered by a large American sewer utility. Employing a conjoint design, we sent customers mailings that varied by medium (postcard vs. letter), frequency, color, sender (government vs. nonprofit), message framing (percentage discount vs. dollar savings), and language (English vs. English-Spanish). Compared to the control group receiving no mail, direct mail significantly increased program inquiries. Notably, postcards were as effective as letters, and sending even one mailing yielded a substantial response increase; additional mailings provided minimal benefit. Sender and message framing had no significant effect. Surprisingly, bilingual mailings resulted in slightly lower response rates. Our findings suggest that direct mailings, particularly postcards, can help improve take-up of income-qualified public assistance programs.