High School Dating
(Bearman, Moody, and Stovel, 2004)
(Image by Mark Newman)


Corporate EMail Communication
(Adamic and Adar, 2005)

Note: This is not the current semester's course Web page.
For current course information, handouts, and homework assignments,
please visit the
present
semester's version of the course.
Networks
Economics 2040 / Sociology 2090 / Computer Science 2850 / Information Science 2040
Cornell University, Spring 2010
MonWedFri 11:1512:05
Statler Auditorium
Note: This is not the current semester's course Web page.
For current course information, handouts, and homework assignments,
please visit the present semester's version of the course.
A course on how the social, technological, and natural worlds are connected,
and how the study of networks sheds light on these connections.
Topics include: how opinions, fads, and political movements
spread through society; the robustness and fragility of food webs
and financial markets; and the technology, economics, and politics
of Web information and online communities.
The course is designed at the introductory undergraduate level
with no formal prerequisites; it satisfies the
Arts & Sciences Social and Behavioral Analysis (SBA) distribution
and the Engineering Liberal Studies (SBA group) distribution.
(See also the
poster announcing the course.)
This is the fourth time the course is being offered;
the home pages for the
Spring 2007,
Spring 2008,
and
Spring 2009
versions of the course are online as well.
See below for more information, including the
class blog,
the outline of topics,
the schedule of office hours,
and the CMS site
(which you can log into using this
CMS link).
Course Staff

Instructors:

Course Staff:
 Vladimir Barash, email: vdb5.
 Ram Dubey, email: rsd28.
 Alex Ainslie, email: ana22.
 Jacob Bank, email: jeb369.
 Burak Bekdemir, email: ab465.
 Eduard Dogaru, email: ed265.
 Ken Ferguson, email: krf39.
 Christie Gibson, email: ceg47.
 Fahad Karim, email: fk66.
 Sameer Nurmohamed, email: sfn4.
 Ozgur Yonter, email: oy32.
Class Blog
CMS Site
At the
CMS site, you can log in with your Cornell NetID to find information
about your course grades and also to upload solutions to homework.
This semester, solutions to all problem sets, as well as the final paper,
must be submitted through the CMS site, by the start of class on
the days they are due.
This means that you should write these up in an electronic format
(Word files, PDF files, and most other formats can be uploaded to CMS).
Also, you should check the CMS site at the start of the semester
to make sure that you are able to log in.
Please let us know if you experience any difficulties with this.
Outline of Topics
(1) Graph Theory and Social Networks
The course begins with a discussion of some of
the general properties of networks.
It develops this through examples from social network analysis,
including the famous ``strength of weak ties'' hypothesis in sociology,
and it connects these themes to recent largescale empirical studies of
online social networks.
Readings (Jan 25  Feb 1)
 Chapters 13 and Chapter 5 of the Networks book draft.
Optional further reading:
 Chapter 2 of The Tipping Point, Sections 15.
(The remainder of the chapter is useful as well, but less
central to the content of the lectures.)
 Mark Granovetter.
The strength of weak ties.
American Journal of Sociology, 78:13601380, 1973.
(This is Granovetter's original paper describing his work
covered in Chapter 3 of the Networks book.)
(2) Game Theory
Since most network studies require us to consider not only
the structure of a network but also the behavior
of the agents that inhabit it, a second important set of
techniques comes from game theory.
This too is introduced in the context of examples, including
the design of auctions and some ``paradoxical'' phenomena
surrounding network traffic congestion.
Readings (Feb 3  Feb 10)
 Chapters 6, 8, and 9 of the Networks book draft. (We will cover Chapter 7 later in the semester.)
Optional further reading:
 Ignacio PalaciosHuerta.
Professionals Play Minimax.
Review of Economic Studies, 70(2003), pp. 395415,
(This is the paper that studies penalty kicks in soccer, as discussed in Section 6.8.)
 Chapter 1 of Micromotives and Macrobehavior.
(3) Markets and Strategic Interaction on Networks
(4) Information Networks and the WorldWide Web
(5) Network Dynamics: Population Models
Networks are powerful conduits for the flow of
information, opinions, beliefs, innovations, and technologies.
We begin by considering how these processes operate at
the level of populations, when we can't necessarily observe
the network itself, but only its effects on aggregate behavior.
As part of this, we consider phenomena including information
cascades, "tipping points" in the success of products with network effects,
and the distribution of popularity.
Readings (Mar 29  Apr 16)
 Chapter 7, Chapters 1618, and Chapter 22 of the Networks book draft.
Optional further reading:
 Introduction and Chapters 1 and 6 of The Tipping Point.
 Chapter 3 of Micromotives and Macrobehavior.
(6) Network Dynamics: Structural Models
We continue our exploration of how things flow through
networks, focusing on what we can learn from details of
the network structure itself.
Here we study how both behaviors and diseases can spread
through a social network, and also some of the network phenomena
that underpin the "six degrees of separation" effect.
Readings (Apr 19  Apr 30)
 Chapters 1921 of the Networks book draft.
Optional further reading:
(7) Institutions and Aggregate Behavior
Finally, a perspective based on networks can provide novel insights
into the structure of social institutions, and
into basic policy questions in many areas.
We illustrate this theme with examples based on markets, voting theory,
and property rights.
Readings (May 3  May 7)
 Chapters 2324 of the Networks book draft.
Books
We will be using a prepublication draft of the book
Networks, Crowds, and Markets, which
we've developed while teaching this course over the past several years.
A complete draft is online at the
Web page for the book,
and a printed version of it is also available through the Campus Store
(for a charge per page to cover the printing costs).
There are also two optional books for the course:
 The Tipping Point: How Little Things Can Make a Big Difference.
Malcolm Gladwell, Little, Brown and Company, 2002.
 Micromotives and Macrobehavior. Thomas C. Schelling, W. W. Nor
ton and Company, 2006.
These two optional books contain material that supplements
and expands on some of the course topics.
Office Hours
 Mon 12:30  1:30: Alex Ainslie, 328B Upson
 Mon 2:00  3:00: Sameer Nurmohamed, 328B Upson
 Mon 3:00  4:00: Jon Kleinberg, 5134 Upson
 Mon 4:00  5:00: Vlad Barash, 368 Uris
 Tue 11:00  12:00: Ken Ferguson, 244 Clark
 Tue 1:15  2:15: Jon Kleinberg, 5134 Upson
 Tue 3:00  4:00: Ozgur Yonter, 328B Upson
 Wed 12:30  1:30: Fahad Karim, 328A Upson
 Wed 1:30  2:30: Burak Bekdemir, 328A Upson
 Wed 2:00  4:00: David Easley, 404 Uris
 Thu 12:00  1:00: Jacob Bank, 328A Upson
 Thu 1:00  2:00: Christie Gibson, 328A Upson
 Thu 3:00  4:00: Eduard Dogaru, 328A Upson
 Fri 9:30  10:30: Ram Dubey, 408 Uris
Prerequisites
Almost no knowledge of specific mathematical content is assumed,
other than some basic probability (random variables, expectation,
independence, and conditional probability),
which we will briefly review when it first arises.
However, the main goal of the course will be
to build mathematical models of the processes that take place in networks.
As such, students will be expected to interpret and work with
mathematical models as they come up the course; at the same time,
students should also think about how to relate these models to
phenomena at a qualitative level.
Coursework
 Midterm: Monday, March 8, in class.
 Final exam: Wed, May 12, 7:00  9:30 pm, Barton Hall.
 Approximately 6 problem sets. As described above,
these must be submitted using the
CMS site, by the start of class on the days they are due.
 A short (46 page) paper due the last week of class. The paper is
designed to be an exploration of a topic related to the course,
containing both a discussion of prior work, and some novel
discussion or analysis of the topic.
Like the problem sets, the final paper must be submitted using the
CMS site.
 Class blog: As discussed above, there is a class weblog and each student
should make two posts to it as part of the graded coursework.
See the accompanying
handout describing the
format and schedule for blog posts.
The
opening blog post describes how to register for the blog and
begin submitting posts.
Grades on homework, the paper, blog posts, the midterm, and
the final will be weighted as follows:
 Midterm: 20%
 Final: 30%
 Homework: 20%
 Short Paper: 20%
 Blog Posts: 10%
Academic Integrity
You are expected to maintain the utmost level of
academic integrity in the course.
Any violation of the code of academic integrity
will be penalized severely.
You are allowed to collaborate on the homework to the extent of
formulating ideas as a group.
However, you must write up the solutions to each problem set completely on
your own, and understand what you are writing.
You must also list the names of everyone that you discussed
the problem set with.
Collaboration is not allowed on the other parts of the coursework.
Finally, plagiarism deserves special mention here. Including text
from other sources in written assignments
without quoting it and providing a proper citation constitutes
plagiarism, and it is a serious form of academic misconduct.
This includes cases in which no full sentence has been copied
from the original source, but large amounts of text have
been closely paraphrased without proper attribution.
To get a better sense for what is allowed, it is highly recommended that
you consult the
guidelines maintained by Cornell on this topic.
It is also worth noting that search engines have
made plagiarism much easier to detect.
This is a very serious issue; instances of plagiarism will very likely
result in failing the course.