PARTITION EFFECTS IN TIPPING
When you order room service in a hotel, the bill often includes a “delivery charge” of a few dollars plus a “service charge” of close to 20%. When you sign the bill, there is always a blank that says “Additional gratuity”.
From a decision science perspective, it would seem odd if people who generally tip less than 20% on deliveries add something to the “additional gratuity” line simply because the tip has been partitioned into two parts: a required 20% part and an “add what you will” part. This similar to the phenomenon of “partition dependence” in the judgment and decision making literature.
The question we had was whether people add an additional gratuity in this situation.
We are not the only ones who had this question. We quickly found a dozen URLs (see URLs at bottom) of forums in which this issue was discussed.
Looking at the forum posts, a few themes recurred:
- People said that it was never clear if the service charge went to the delivery person (making it the gratuity) or to the hotel or if it was spread around.
- People who did not tip extra tended to be stronger in their opinions than those who did.
- People who did tip extra tended to say they’d add about two dollars, usually in cash.
- Websites varied in their proportion of respondents who tip extra.
To the last point, we combed through the forums and coded as many posts as we could as pro- or con- tipping extra. The results are below, where each row has the syntax:
WEBSITE: #_TIPPING_EXTRA / #_RELEVANT_COMMENTS = %_TIPPING_EXTRA
Fodors: 5 / 23 = 21%
Chowhound: 10 / 23 = 43%
Hotelchatter: 1 / 5 = 20%
Metafilter: 3 / 11 = 27%
Milepoint: 7 / 16 = 44%
Datalounge: 2 / 4 = 50%
Yahoo Answers: 2 / 11 = 18%
Flyertalk: 7 / 19 = 37%
Adding this all together we get:
Grand Total 37 / 112 = 33% tipping extra
Because generosity is socially desirable, those who do tip extra may be more likely to comment than those who don’t. This selection effect would suggest 33% is too high. On the other hand, there may be a sets of people who do add an additional tip for various reasons (e.g. due to misunderstanding, generosity, or being well off) but don’t participate in forums for various reasons. This would suggest that 33% is too low. We’re not comfortable guessing in which direction our estimate is biased.
Suppose that a third of people do tip more when the tip is partitioned than when it’s not. How far this can be pushed? Would it go up if the bill read as follows?
Delivery charge: $5
Base Service charge: 15%
Supplemental Service charge: 10%
Additional Gratuity: ________
- When coding the forum posts, we tried to capture what people most always do. We tried to ignore comments that said things like “it depends” or dodged the question. As we got tired, we may have drifted in our coding policy a bit.
- If you want to read something funny about hidden fees, see Ian Frazier’s “From the Bank with Your Money on Its Mind“.
- If you want to read another DSN post on tipping, see: Tipping Heuristics
URLS OF FORUMS DISCUSSING TIPPING EXTRA