Over the last several years, BPL streamlined our card signup process, making it much easier to get a library card both online and in person. We also expanded our marketing, advertising, and social media presence. And while our average monthly card signups had significantly increased compared to prior years, we noticed that some areas of Brooklyn had persistently low cardholder rates.
Working with the NYC Behavioral Design Team, ideas42, we conducted surveys and interviews of current cardholders, past cardholders, and those who never had a card. We found that many adults who had never had a BPL card associated libraries with services for children and students, limiting the library’s perceived relevance. Our research also highlighted that many adult patrons first connect with BPL or are inspired to return after years without a card through community word-of-mouth.
With ideas42, we began brainstorming ways to increase adult card signups that addressed these findings.

Invite-a-Friend is a referral campaign where cardholders can invite people in their networks to sign up for a library card and earn BPL-branded gifts as thanks. It leverages word-of-mouth to bring in new patrons who would not otherwise have signed up, without the encouragement from someone they know and trust.
During the campaign, when BPL patrons logged into their account they saw a new page with their unique referral link and prompts on how to send to friends, highlighting unique BPL services. The links went to BPL’s usual library card application, but allowed us to give credit back to the referrer. If the application was completed, the referrer’s account automatically updated to show them what they earned from our three gift tiers. At the end of the promotion, patrons who earned gifts got instructions on how to redeem the gifts for free via our online store.
Unlike other referral programs, we did not ask patrons to input friends’ contact information, protecting their privacy.

We piloted Invite-a-Friend during April 2026 and during that time we received 2,422 new card applications from 1,220 unique referrers, contributing to an 18% increase in total card signups the month of the pilot compared to the previous month.
Compared to proxy baselines, Invite-a-Friend generated an increase in card signups across Brooklyn, including our target ZIP codes with low per capita cardholder rates. We also signed up a much higher proportion of younger adults (ages 23-37) than usual.
Staff were able to participate as referrers, and enjoyed striving to get all three gifts. Our top two staff members each got 13 friends to apply!
We received a lot of positive feedback from patrons on the campaign who were eager to spread the word about BPL. One patron wrote in to say: "Thank you for this amazing offer, it was fun to talk to friends and family about joining, and the merch is great."