Archive for November, 2006

Splitting Ravioli

2006 November 12

(or: “Danny and Bethany jump the shark”)

Bethany and I had Ravioli tonight. Afterwards, there was a little left in the pot. Five pieces, to be exact. We usually use yootles for binary decisions (say, which one of gets the last portion of ravioli) but in this case, Bethany wasn’t sure she wanted all of it. What, we wondered, was the socially optimal division of the ravioli?
We decided we wouldn’t be risking much social efficiency by discretizing this decision into 6 options, characterized by how many pieces I (Danny) would get. We submitted our bids at as follows:

Danny:   ybid ravsplit r0 0  r1 .2  r2 .4  r3 .6  r4 .8  r5 1
Bethany: ybid ravsplit r0 .67  r1 .67  r2 .5  r3 .33  r4 .23  r5 0

These are graphed below, with my utility as a function of number of pieces graphed in blue, Bethany’s in pink, and the mean utility (i.e., half the aggregate utility) in black.

Splitting Ravioli

As you’d expect, the Decision Auction (DAUC) made the socially optimal choice of giving me four pieces of ravioli and Bethany one, charging me Y$0.235.


Yootles Trivia Question

2006 November 7

The first person who can answer the following question (add a comment!) gets 10 yootles (or $10 if you prefer):

In a yootles ledger system, can someone gain an advantage by creating many fake identities who all extend credit to their real identity?

New Protocol for Offering and Asking for Favors

2006 November 4

Bethany and I have adopted a new protocol for offering and asking for
favors. For example, Bethany forgot her wallet at home the other day so
was stuck at school without means to procure food.


Here’s the old way:

  • D: Forgot your wallet? I can skate uptown and bring you some cash!
  • B: That’s ok, you’re busy, and I’ll go home after class anyway.
  • D: I don’t mind, I need a break anyway.
  • B: But I really don’t need it that bad.
  • etc. We’re stuck in “want” vs “really want” land.

New way:

  • D: Being so magnanimous, I’ll *share* the task of bringing you cash!
  • B: That’s sweet! I’ll place a bid on ‘bwallet’ at
  • B enters, for example, ‘ybid bwallet -12’. (The default Decision Auction is used.)
  • Now either it would cost me more than that (e.g., I enter
    ybid bwallet -16) and I’m off the hook but give Bethany yootles, or it
    would cost me less and I do the favor but get paid yootles.

It seems strange to give Bethany yootles because she forgot her wallet but
it’s by construction less skin off my nose than schlepping uptown for her.
The favor is to make it half my responsibility so once that’s been
established it’s only fair that whoever gets out of it gives some yootles
to the person who actually does it.

That’s the beauty of this protocol. I can offer to help and have it be a
Genuinely Generous Gesture, even if it doesn’t make sense (is not socially
optimal) for me to actually deliver on the favor.


If you’re asking for a favor you say “let’s have an auction to see if it
would be socially efficient for you to do X for me.” For example, I asked
Bethany if she’d mind (less than me) rotating my skate wheels. It was
no skin off her nose to bid in the auction — just bid truthfully and the
auction will only make her do it if she gets enough yootles to *want*
to do it (she didn’t). This is done with a Favor Auction (go to or text ‘ymech fav’ to 4INFO (44636) to learn
how to use it).

In a Favor Auction, the default is that the favor does not happen and no payments are made, but if it’s socially optimal to do the favor then the favor seeker(s) pay the favor provider(s) to do it.
That’s in contrast to a Decision Auction where it’s assumed up front that a task has to get done. Everyone takes equal responsibility and it’s just a matter of deciding who does it.