How Charity Navigator Used AddEvent to Drive a 45% Lift in Donor Conversions customer success

Charity Navigator, America’s premier nonprofit rating organization, partnered with researchers from Maastricht University in the Netherlands to run a rigorous experiment ahead of GivingTuesday in 2025. The goal was simple: understand which donor engagement tactics actually move people to give. 

Among the strategies tested, including hard pledge forms, early giving appeals, and calendar reminders via AddEvent, the results were clear. Getting donors to add GivingTuesday to their calendars increased conversions by 45% compared to an untreated control group. The Add to Calendar group matched the performance of the “give now” early donation appeal and outperformed a hard pledge ask by 25%. The experiment has reshaped how Charity Navigator thinks about donor communications and sparked plans to potentially leverage calendar marketing as a new channel in the coming year.

The Challenge

Charity Navigator, a 501(c)(3) organization, evaluates and rates more than 1.7 million U.S. nonprofits to help donors give with confidence. Kyle Gardner, SVP of Development at Charity Navigator, was no stranger to the perennial fundraising puzzle: how do you actually move lapsed or never-converted donors to take action on a major donation day like GivingTuesday?

But like many nonprofits, Charity Navigator struggled to activate two specific, high-value donor segments: people who had subscribed to their emails and shown interest but had never made a donation, and lapsed donors who hadn’t given in the past 3 years. Despite their best efforts, standard email campaigns weren’t enough to break through.

When a researcher from Maastricht University approached Charity Navigator about running a controlled giving experiment, the team saw an opportunity. The original proposal was overly complex; it centered on a hard pledge mechanism that asked donors to pre-commit to a specific dollar amount before GivingTuesday. Gardner pushed for a simpler, more practical test.

“We needed an easier call to action. The pledge form was too much of a hard sell. We wanted to find out what actually moves people, not just what looks good on paper.”

— Kyle Gardner, SVP Development, Charity Navigator

The Solution

Gardner and his team designed a four-arm experiment across two Charity Navigator donor segments, reaching over 65,000 people total. Each group received three identical emails throughout November, one in early November, one mid-month, and one at the end of the month, each containing the same call to action tied to their assigned treatment group.

The four treatment conditions were:

A – Hard Pledge: Donors were directed to a submission form asking them to commit to a specific GivingTuesday donation amount in advance.

B – Add to Calendar via AddEvent: Donors were invited to add GivingTuesday as a calendar reminder. Kyle set up the event intentionally to run from 8:00 AM to 11:59 PM local time—deliberately avoiding an all-day format that can get buried at the top of a calendar view.

C – Give Now: Donors were asked to make their donation immediately: Why wait for GivingTuesday?

D – Holdout (No Treatment): A control group that received none of the campaign emails.

Implementation via AddEvent was seamless. The calendar event’s description linked directly to Charity Navigator’s website, and because donors used the same email address across touchpoints, the team was able to attribute giving behavior holistically rather than relying solely on last-click tracking, capturing a more accurate picture of how the campaign primed donors to act.

“I set it up so it appeared on their calendar from 8 AM local to 11:59 PM local. I always worry that if you try to add it as an all-day event, it just appears on the top bar of a calendar—too easy to miss.”

— Kyle Gardner, SVP Development, Charity Navigator

The Results

The results validated what Kyle had suspected: getting on donors’ calendars is one of the highest-leverage moves a fundraising team can make.

Across both donor segments (never-converted Charity Navigator subscribers and lapsed donors), the Add to Calendar (AddEvent) treatment and the Give Now treatment performed nearly identically, each delivering a 45% lift in giving behavior compared to the untreated holdout group.

The experiment was shared publicly on LinkedIn under Kyle’s #MondayFundraisingThoughts series, reinforcing what the data had already shown: fundraisers are hungry for tactics that actually work.

“Get donors to add a special day of giving reminder to their calendar and/or make the case to give in advance. Those are your two winners.”

— Kyle Gardner, SVP Development, Charity Navigator

Looking Ahead

This initial experiment represents just the starting point for broader adoption. There are plans to expand the use of Add to Calendar as a consistent tactic during key fundraising moments throughout the year, particularly during high-impact periods when a significant portion of annual giving occurs within a short timeframe.

There is also interest in exploring Subscription Calendars as a way to address declining return visits to websites. Every day it is becoming more and more important to build direct, owned channels rather than relying on algorithms that change on a whim. Tapping into calendar marketing (not to be confused with a marketing calendar) allows supporters to opt into a Subscription Calendar once and automatically receive future events and reminders. Calendar marketing offers a high-retention approach that bypasses crowded email inboxes and social feeds.

As Charity Navigator continues to test and expand their use of Add to Calendar and calendar marketing, AddEvent will be alongside them to support and power its efforts.

“Each time we’re inviting people to an event, we’re losing out by not having a way for them to subscribe to the whole calendar. If we just get them to do that once, it could be huge.”

— Kyle Gardner, SVP Development, Charity Navigator