About

Hi! My name is Stylianos DespotakisGreek: Στυλιανός Δεσποτάκης, pronounced [stiʎa'nos ðespo'takis] steel-yah-NOHSS theh-spoh-TAH-kees. I usually go by SteliosGreek: Στέλιος, pronounced ['steʎos] STELL-yohs. I am a PhD student at Carnegie Mellon University's Tepper School of Business, where I am advised by R. Ravi.

Research Interests

My research interests lie in the interdisciplinary area of game theory, marketing, microeconomics, and operations research.

Education

August 2012–present
Carnegie Mellon University, Pittsburgh, PA, USA
PhD, Dissertation Committee: R. Ravi (chair), Kannan Srinivasan, Vibhanshu Abhishek, Isa Hafalir, and Kaifu Zhang
August 2012–May 2014
Carnegie Mellon University, Pittsburgh, PA, USA
September 2010–July 2012
MSc in Logic, Algorithms, and Computation
GPA: 10.00/10.00 (ranked 1st in my year)
September 2006–June 2010
BSc in Mathematics
GPA: 9.56/10.00 (ranked 1st in my year)
September 2003–June 2006
Pefka High School, Thessaloniki, Greece
GPA: 19.5/20.0

Research Papers

Auctions
Online Appendix

Abstract

We examine the effect of the presence of expert buyers on other buyers, the platform, and the sellers in online markets. We model buyer expertise as the ability to accurately predict the quality, or condition, of an item, modeled as its common value. We show that non-experts may bid more aggressively, even above their expected valuation, to compensate for their lack of information. As a consequence, we obtain two interesting implications. First, auctions with a hard close may generate higher revenue than those with a soft close. Second, contrary to the linkage principle, an auction platform may obtain a higher revenue by hiding the item's common-value information from the buyers. We also consider markets where both auctions and posted prices are available and show that the presence of experts allows the sellers of high quality items to signal their quality by choosing to sell via auctions.

Attribution
(under review)  

Abstract

In this paper, we study the problem of attributing credit for customer acquisition to different components of a digital marketing campaign using an analytical model. We investigate attribution contracts through which an advertiser tries to incentivize two publishers that affect customer acquisition. We situate such contracts in a two-stage marketing funnel, where the publishers should coordinate their efforts to drive conversions.

First, we analyze the popular class of multi-touch contracts where the principal splits the attribution among publishers using fixed weights depending on their position. Our first result shows the following counterintuitive property of optimal multi-touch contracts: higher credit is given to the portion of the funnel where the existing baseline conversion rate is higher. Next, we show that social welfare maximizing contracts can sometimes have even higher conversion rate than optimal multi-touch contracts, highlighting a prisoners' dilemma effect in the equilibrium for the multi-touch contract. While multi-touch attribution is not globally optimal, there are linear contracts that "coordinate the funnel" to achieve optimal revenue. However, such optimal-revenue contracts require knowledge of the baseline conversion rates by the principal. When this information is not available, we propose a new class of 'reinforcement' contracts and show that for a large range of model parameters these contracts yield better revenue than multi-touch.

Adblocking
The Beneficial Effects of Ad Blockers
(working paper)
Network
Advertising of Products with Positive Network Effects
(work in progress)

Honors and Awards

2015 Winner (team of two) of the SMART Workshop Structural Modeling Challenge, Carnegie Mellon University
2014 Egon Balas Award for the Best paper in Operations Research / Algorithms, Combinatorics & Optimization, Carnegie Mellon University
2012–2016 William Larimer Mellon Fellowship, Carnegie Mellon University
2010–2011 Mytilinaios Prize for ranking 1st among the students of the Logic, Algorithms, and Computation graduate program
2008–2010 Thomas Papamichailidis Scholarship for ranking 1st among the students of the Faculty of Sciences and the Faculty of Engineering (2 years)
2006–2010 Four Awards from the State Scholarships Foundation (IKY) for ranking 1st among the students of the Department of Mathematics
2006 First member of the national team at the 23rd Balkan Mathematical Olympiad
2006 Gold Medal at the 23rd National Mathematical Olympiad
2005 Bronze Medal at the 22nd National Mathematical Olympiad
2002–2005 Two First Prizes and two Honorable mentions at the National Mathematical Competition Euclid held by the Hellenic Mathematical Society

Teaching Experience

Co-instructor for
  • Optimization for Interactive Marketing, Tepper 45-853, MBA, Fall 2016
Teaching Assistant for
  • Optimization for Interactive Marketing, Tepper 45-853, MBA, Spring 2016
  • Business Networks, Tepper 45-951, MBA, Fall 2015
  • Business Networks, Tepper 45-951, MBA, Fall 2014
  • Linear Programming, Tepper 47-834, PhD, Fall 2014
  • Optimization, Tepper 45-751, MBA, Spring 2014
  • Graph Theory, Tepper 47-835, PhD, Fall 2013
  • Applications of Operations Research, Tepper 45-850, MBA, Fall 2013

Graduate Coursework (selected)

  • Fall 2015: Econometrics I (47-811)
  • Spring 2015: Analytical and Structural Marketing Models (47-744)
  • Fall 2014: Advanced Stochastic Analysis and Applications I (47-774), Advanced Stochastic Analysis and Applications II (47-775)
  • Spring 2014: Random Graphs (21-801)
  • Fall 2013: A Theorist's Toolkit (15-859), Real Analysis (21-620), Introduction to Lebesgue Integration (21-621)
  • Spring 2013: Graduate Algorithms (15-750), Algorithms Games and Networks (15-896), Integer Programming (47-830), Advanced Integer Programming (47-831)
  • Fall 2012: Discrete Mathematics (21-701), Linear Programming (47-834), Graph Theory (47-835), Networks and Matchings (47-836), Dynamic Programming (47-840)
  • Fall 2011: Computational Game Theory, Computational Algebra, Advanced Approximation Algorithms
  • Spring 2011: Mathematical Logic, Algorithms and Complexity II, Set Theory, Approximation Algorithms
  • Fall 2010: Computability, Algorithms and Complexity I, Graph Theory, Cryptography and Complexity

Computer Skills

Mathematica, C/C++, Python, R, HTML/CSS, Javascript (jQuery), LaTeX, Cambridge IT Skills Proficiency

Other Activities

  • Chess: I was an active member of the Pefka Chess Club during the period 2002–2006 (participating in tournaments with many distinctions).
  • Solving algorithmic and mathematical problems (e.g. ranked 1st in the world on ProjectEuler.net in December 2008 after solving all 221 problems by then).