Proc. Natl Acad. Sci. USA 115, 939–944 (2018)

When immigrants attain citizenship through naturalization, individuals and the community benefit economically. Nevertheless, the rate of naturalization applications in the United States has been in decline. What measures can increase citizenship applications?

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Jens Hainmueller, of Stanford University, and colleagues addressed this question in two randomized controlled trials targeting low-income, naturalization-eligible immigrants in New York who had previously registered interest in naturalization. In the first trial, a randomly selected group received a voucher to waive the $680 application fee. In the second trial, people whose income was low enough that fees were automatically waived did not receive a voucher, but instead received either different ‘nudges’, such as cover of transport costs to the next Opportunity Center or text message reminders, or not.

Waiving the fee for immigrants who would otherwise have to pay approximately doubled application rates to 78%. The different nudges had no such effect. This shows that while financial hurdles affect application rates, other factors must be at play to explain the ineffectiveness of nudges for the very poor.

The research has implications for policymaking. It also highlights that nudges, often shown to be powerful modifiers of behaviour, can be ineffective. It’s important for future research to identify which type of nudge works best in specific cases.