Mette Trier Damgaard and Christina Gravert sent appeals by email and text to roughly 53,000 prior donors of DanChurchAid and randomly varied the deadline: a few days, about ten days, or more than a month. Published in the Journal of Behavioral and Experimental Economics in 2017, the result was blunt. The length of the deadline had no effect on whether people gave. Gifts spiked on the day the message landed and fell to almost nothing within two or three days, whatever the deadline said. The authors called it a "now or never" effect. In their working paper, only about 11 percent of text-message gifts in the long-deadline group arrived after day three.

So the obvious move is a reminder, and reminders work. In a follow-up with the same charity, the two researchers sent 17,000 newsletter subscribers an appeal, and half of them a reminder a week later. The reminder raised one-time donations by 66 percent. It also raised unsubscribes by 76 percent. When they modeled what those lost subscribers would have given in future years, the reminder cut the total value of the campaign by about a third. Their paper in the Journal of Public Economics (2018) is titled, accurately, "The hidden costs of nudging."

Then the finding that turns the whole problem sideways. James Andreoni and Marta Serra-Garcia asked people to give five dollars to charity. When the money would leave today, about 30 percent said yes. When the same five dollars would be paid in one week, giving rose by 50 percent (published in the Journal of Public Economics in 2021). Standard self-control models predict the opposite. Their explanation: the good feeling of giving arrives the moment you decide, not the moment you pay. Moving the payment later lets people collect that feeling now and defer the cost.

Put those three together and the donor's week looks very different from our calendar. The decision window is short. A second nudge reopens it, at a price. And the yes itself can be separated from the money, which is a gift if you design for it and a leak if you don't.

Samuel McClure, David Laibson, George Loewenstein and Jonathan Cohen scanned people choosing between smaller rewards now and larger ones later, published in Science in 2004. Options available right now lit up the brain's core reward system. Choices of every kind engaged the slower planning regions in the front and side of the brain, and those regions were relatively more active when people chose to wait. It's a simplification to call it two brains fighting, and later work has softened the picture. But the useful part holds: "now" has a privileged line into the reward system that "later" does not.

That explains the now-or-never curve. When your email lands, the cause is vivid, the story is in front of the donor, and the warm glow I write about in Neurogiving is available immediately. Two days later the email is below the fold, the feeling has faded, and what remains is a to-do. To-dos are the planning system's job, and the planning system has a dozen other items it considers more urgent than yours.

It also explains the Andreoni and Serra-Garcia puzzle. The warm glow is paid out at the moment of commitment. If the cost can wait, the "now" system gets its reward and the "later" system inherits a bill it was never consulted about. That's why pay-later pledges raise yeses. It's also why so many of them never get paid, which is where Pro picks up this week.

This week, a perceptual reframe and one thing to look at before your year-end plan locks.

Stop thinking of your deadline as the end of the campaign. Think of every send as its own three-day campaign with its own beginning, middle and end. The deadline doesn't create urgency. The arrival does. Which means the question isn't "how many days until midnight on the 31st?" It's "how many arrivals is this donor going to experience, and is each one worth what it costs?"

So pull last year's year-end results and plot gifts by day for each send separately, not the campaign total. If your file behaves like the Danish one, you'll see a set of sharp peaks that decay within about 72 hours, not a slow build toward December 31. Then lay your unsubscribe and spam-complaint data on the same chart. If each additional send produces a smaller peak and a larger unsubscribe bump, you've found the exact point where your reminders started borrowing from next year.

One more design choice is worth considering before you finalize the plan: for a segment of donors who've told you they give at year-end, offer a way to say yes now and schedule the gift for a date they choose. The research says more people will say yes. Pro covers what it takes to make sure the yes turns into money.

Research Sources

In Lab Notes Pro

I left one question hanging on purpose. If more people say yes when the money can wait, how many of those yeses ever turn into gifts? Pro has the answer, and how to close the gap. Fair warning: you won’t count a “verbal commitment” the same way again.

You’ll also find out why “give them more time” can backfire, when your December non-responders may be most ready to say yes, and which three year-end habits look like wins in December but cost you later. (At least one is probably on your calendar already.) Then there’s a test you can set up in one afternoon that answers a question worth taking to your board: are your December reminders paying for themselves, or borrowing from next year?

Full disclosure: I’m about to use this week’s research on you.

You just read that people say yes more often when the cost comes later, because the good feeling arrives with the decision. So Lab Notes Pro now comes with a 14-day free trial. Say yes today, and this week’s full Pro issue is yours right away, along with every back issue. You pay nothing for two weeks.

Here’s how it works, with no fine print. You’ll add a card when you start. When the 14 days are up, your membership continues at $9 a month or $90 a year, depending on the plan you pick. You’ll have access to all the Pro archives and an office hour call. If Pro isn’t earning its place, cancel and you won’t be charged. I’ll send you a reminder on day 12. I’d rather you stay because Pro earned it than because you forgot.

And you know what this week’s research says about “I’ll come back to it later.”