Ayres grew up in Kansas City, Missouri, where he graduated from Pembroke Country Day School in 1977. He played varsity basketball, ran cross country, and served as executive editor of his high school newspaper. Ayres wrote an op-ed piece his senior year called "Black Like Me" (named for the 1961 book of the same name), a controversial piece detailing the consequences of his checking the "African- American" box for race on his PSAT, which led to consideration for academic awards. Ayres graduated summa cum laude in 1981 from Yale University with a dual degree in Russian studies and economics. He then received his J.D. at Yale Law School in 1986, where he was an editor of the Yale Law Journal. He received his Ph.D. in economics at the Massachusetts Institute of Technology in 1988.
Ayres has taught at Northwestern University School of Law, the University of Virginia School of Law, the Moscow State Institute of International Relations Cardoza Law Institute, the University of Iowa College of Law, the University of Illinois College of Law, Stanford Law School, the University of Toronto Law School, and Yale University.
Since 1994, Ayres has served as the William K. Townsend professor at the Yale Law School and is a professor at the Yale School of Management. He teaches antitrust, civil rights, commercial law, contracts, corporations, corporate finance, law and economics, property, and quantitative methods. In 2006, Ayres was elected a fellow of the American Academy of Arts and Sciences, and also currently serves as a research associate at the National Bureau of Economic Research, and as editor of the Journal of Law, Economics and Organization. Ayres has previously served as a research fellow of the American Bar Foundation and has clerked for James K. Logan of the Tenth Circuit Court of Appeals. In a post-conviction petition, Ayres was successful in vacating the death sentence for his client.
Ayres has published eight books and over 100 articles in law reviews and magazines on a variety of subjects, and has been ranked as one of the 250 most prolific and most-cited legal scholars of his generation.
In 2007, Ayres co-founded StickK, a web startup enabling users to enter commitment contracts to reach personal goals.
In a September 2007 review of Ayres' book Super Crunchers, the New York Times' David Leonhardt wrote that he "came across two sentences about a doctor in Atlanta that were nearly identical to two sentences I wrote in this newspaper last year."  On October 4, the Yale Daily News reported that it had found nine passages in the book that were identical or similar to those in the Times and four other publications. In reference to Ayres' case and a similar one in Illinois, George Washington University professor of English, Margaret Soltan, said: "Both men simply stuck passages from other writers into their text when it suited them, and gave either minimal or no attribution. In some of the passages in question, neither used quotation marks, even when they quoted at length, verbatim."
Although Ayres and his publisher, Bantam Dell, said that his endnotes were satisfactory, Ayres apologized and said: "in several brief instances in the book, my language is too close to the sourced material and I should have used quotation marks to set it apart from my text." He and his publisher promised to correct future printings. Other academics were not satisfied with the explanation that Ayres had simply made a mistake, nor did they accept that such practices were acceptable in popular books. Soltan wrote that the same behavior by students is "severely sanctioned." Columbia law professor Michael Dorf asked if the "scandal" was one of research-assistant ghostwriting rather than plagiarism.
Ian Ayres’ books include:
- The $500 Diet: Weight Loss for People Who Are Committed to Change(Kindle Singles, 2011)
- Carrots and Sticks (Bantam, 2010, ISBN 0-553-80763-3)
- LifeCycle investing: A New, Safe, and Audacious Way to Improve the Performance of Your Retirement Portfolio, with Barry Nalebuff (Basic Books, 2010, ISBN 0-465-01829-7)
- Studies in Contract Law, with Richard E. Speidel (Foundation Press, 2008, ISBN 1-59941-255-1)
- Super Crunchers: Why Thinking-By-Numbers is the New Way To Be Smart (Bantam, 2007, ISBN 0-553-80540-1)
- Straightforward: How to Mobilize Heterosexual Support for Gay Rights, with Jennifer Gerarda Brown (Princeton University Press, 2005, ISBN 0-691-12134-6)
- Optional Law: The Structure of Legal Entitlements (University of Chicago Press, 2005, ISBN 0-226-03346-5)
- Insincere Promises: The Law of Misrepresented Intent, with Gregory Klass (Yale University Press, 2005, ISBN 0-300-10675-0)
- Why Not?: How to Use Everyday Ingenuity to Solve Problems Big and Small, with Barry Nalebuff (Harvard Business School Press, 2003, ISBN 1-59139-153-9)
- Voting with Dollars: A New Paradigm for Campaign Finance, with Bruce Ackerman (Yale University Press, 2002, ISBN 0-300-09262-8)
- Pervasive Prejudice?: Non-Traditional Evidence of Race and Gender Discrimination (University of Chicago Press, 2001, ISBN 0-226-03351-1)
Ian Ayres’ two most well-known articles are:
- “Fair Driving: Gender and Race Discrimination in Retail Car Negotiations”, 104 Harvard Law Review 817 (1991)
- “Filling Gaps in Incomplete Contracts: An Economic Theory of Default Rules”, with Robert Gertner, 99 Yale Law Journal 87 (1989)
- "Ian Ayres - Yale Law School". law.yale.edu. Yale Law School. 2014. Retrieved March 18, 2014.
- Conniff, Richard (May 2004). "Flipping It". Yale Alumni Magazine. Archived from the original on February 7, 2005. Retrieved May 20, 2009.
- "Yale Law Journal". Yale Law School 95 (4). March 1986.
- "Book of Members, 1780-2010: Chapter A". American Academy of Arts and Sciences. Retrieved 28 April 2011.
- Ian Ayres (August 27, 2013). "About Ian Ayres". islandia.law.yale.edu/. Ian Ayres. Retrieved March 18, 2014.
- James Lindgren and Daniel Seltzer, "The Most Prolific Law Professors and Faculties," 71 CHI.-KENT L.REV.781 (1996); Fred R. Shapiro, "The Most-Cited Legal Scholars," 29 J.LEGAL STUD.409 (2000)
- Leonhardt, David (September 16, 2007). "Let’s Go to the Stats". New York Times. Retrieved May 20, 2009.
- Torbati, June (October 4, 2007). "Law prof. borrows text for book". Yale Daily News (New Haven, Connecticut).
- Soltan, Margaret (October 8, 2007). "Plagiarism: Yours, Mine, and Ayres'". insidehighered.com (Blog). University Diaries. Inside Higher Ed.
- Dorf, Michael (October 4, 2007). "Harvard Law 3, Yale Law 1: Plagiarism or Ghostwriting?". dorfonlaw.org (Blog). Michael Dorf.
- Ian Ayres' official website
- Why Not? How to Use Everday Ingenuity to Solve Problems Big and Small, with Ian Ayres and Barry Nalebuff
- Ayres uncovers hidden bias in racial stats in the Harvard Law Record
- Roberts, Russ (October 22, 2007). "Ayres on Super Crunchers and the Power of Data". EconTalk. Library of Economics and Liberty.