Tha Matching Theorem in Spliddit
Have you ever felt awkward talking about splitting rent with roommates, taxi fares with friends, credits with research partners, etc.? These are some common scenarios that we encounter in daily life. Take me as an example, my roommate and I are living in a 2B2B at CTT this year. We selected our room before arrival because the room map appears that these two rooms are the same size. When we arrived, we found that both of my roommate’s bedroom and bathroom is slightly larger than mine. However, we separate the bill evenly. Feeling awkward to point out, we just stuck to the original plan. After I took this class, I realized that The Matching Theorem is a good way to approach this problem and I found a website called Spliddit, which made perfect for solving such problems fairly and efficiently.
When you start a page for sharing the rent on Spliddit, you can input the monthly rent, roommates’ names, and rooms’ names. Then, each roommate can evaluate the rooms by bidding on how much they would pay for each room. The total amount of each one’s bids should be equal to the monthly rent. My roommate and I just used this tool and received the following result:
My roommate
Small Room: $ 950
Big Room: $ 1300
Total: $ 2250
Me
Small Room: $ 1050
Big Room: $ 1200
Total: $ 2250
Result
My Roommate Big Room
$1250
Me
Small Room $1000
From the above result, my roommate got the big room she wants by paying $1250. I got the small room by paying $1000. Although I did not get the big room that I hope for, Spliddit convinced me with the explanation: “Why is my assignment envy-free? You were assigned the room called ‘Small Room’ for $1000.00. Since you valued the room at $1050.00, you gained $50.00. You valued the room called ‘Big Room’ at $1200.00. Since this room costs $1250.00, you would have lost $50.00.” The way that Spliddit works resembles the Valuations examples that we learned in class. Since the market-clearing prices can resolve the contention in this issue, changing the prices can interfere with my preference. I do not care about having a Big Room than my roommate does, so I would be satisfied when my rent for the Small Room gets lower than I expected. Therefore, when the market clears, we can reach an agreement by getting what we most valued. Spliddit can help to resolve any problems fairly, ranging from splitting taxi fares to research credits.
In the end, I would like to give some advice for improving Spliddit. In my case of splitting rent fee, we have a small bedroom, a small bathroom, a big bedroom, and a big bathroom. So, I wanted to have four items to bid for, but Spliddit does not support two people bidding for four rooms. It would be useful to take this into account.
Sources:
http://www.spliddit.org/
https://dl.acm.org/doi/10.1145/2728732.2728738
https://www.geekwire.com/2015/dont-fight-over-the-check-spliddit-helps-you-split-expenses/