A website founded by three Yalies is dedicated to helping people keep resolutions.

Roughly four years after two Yale professors and a student in the Yale School of Management launched stickK.com, a website that lets people impose monetary penalties on themselves if they fail to keep their promises, the service has more than 150,000 users, including upwards of 300 affiliated with the University. According to Sam Espinosa ’06, Director of Marketing at stickK, the website is currently focusing on integrating the services of high-tech companies to make it easier for people to report their successes and more difficult for them to falsify their progress. One Yale student who used stickK praised the service for its effectiveness but added that he might only enter into a new contract if he knew beforehand that he could complete it.

StickK is a free online service that offers “commitment contracts,” or agreements to accomplish some task by a certain date or else face potential monetary or social punishment. The website has a handful of preset goals, including “Lose Weight,” “Exercise Regularly” and “Quit Smoking,” but the users have the ability to define their own objectives, a feature that Ian Ayres ’81 LAW ’86, stickK Co-Founder and professor at the Yale Law School and the Yale School of Management, said contributes to the popularity of the service.

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“I have read about 10,000 of the self-designed commitments and they cover such a wide range of human emotion and behavior,” he said. “Some people committed to gain weight, others to lose weights. Some people committed to quit playing video games, some people committed to get to the next level on their PS2 Warcraft game. You just see this whole arch of human struggle.”

According to Espinosa, stickK contracts become increasingly more effective as they hold people more accountable for their resolutions. While agreements without any form of potential punishment succeed only 29 percent of the time, adding a “referee” — a friend or family member to monitor and record progress on the website — brings the success rate to 59 percent.

Monetary incentives further increase the success rate of resolutions. Contracts can stipulate one of three types of fines for failure: giving money to a particular person, to a charity, or to an “anti-charity” — a group that the user dislikes. Suggested anti-charities range from the NRA Foundation and Freedom to Marry to American lobbying organizations to the English Premier League Fan Clubs. Espinosa said the success rates was around 80 percent for contracts that include an anti-charity clause.

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Carl Chauvin ’12 structured his stickK contract with a monetary incentive: after three years rowing for the varsity crew team, he quit last spring but wanted to stay in shape. He heard about stickK from Louis Gilbert ’12, who interned at the company last summer, and decided to enter into an eight-week contract at the beginning of the fall that said that he would have to pay his brother $20 for every week in which he exercised fewer than four days. Chauvin said he only missed his goal once in eight weeks.

“I had a great experience with it,” he said. “I thought it helped me a lot, and if there is something I want to do that I think is going to be hard to motivate myself to do, I would definitely use it again.”

However, Chauvin said that he has not been as diligent about working out since the stickK contract expired a few months ago. While tempted to enter into another agreement, he said that is not sure if he has the motivation to justify signing a new contract, given the financial risk of failure.

Ayres said that even people who were certain to fulfill their resolutions might use stickK as a way to demonstrate, to themselves or others, that they are serious about their goals.

“It’s kind of internal insurance,” Ayres said. “Even if you believe you are likely to do it, it’s a way to back up to yourself and possibly to others that you really intend to do this.”

Each time an individual breaks a contract that involves a penalty fee, stickK collects a percentage of that fee. Ayres said stickK collects 19.5 percent of contract defaults to charities and 29.5 percent to anti-charities.

StickK’s other major revenue source is its corporate contracts. In the fall of 2010 stickK began to offer commitment contracts for companies that wanted to encourage certain employee behavior. Employees that meet goals, such as arriving to work on time, earn points in a reward store. StickK currently has about 15 companies enrolled in the program, and Espinosa said that stickK hopes to grow this pool, since companies, unlike individuals, pay to offer stickK’s service to their employees.

Since so much of the reporting on users’ progress comes from friends of clients, stickK faces the issue of making sure that their reports are reliable, but Gilbert said that stickK’s growing partnership with third-party developers has helped it enforce contracts. For instance, while people might have once lied about their weight when entering it online, stickK’s recent integration with an Internet-connected scale makes it harder for users to fake the data. According to Espinosa, stickK plants to collaborate with other services, including the exercise application “CardioTrainer” and the location-based social network “Foursquare,” to help monitor progress on resolutions.

In addition to Ayres, stickK’s founding team included economics professor Dean Karlan and Jordan Goldberg ’06, then a student at SOM and the current CEO of stickK.