Why Do You Lie? The Perils of Self-Reporting

I am always surprised at how easily, and cheaply, we humans lie.

Have you ever been in a conversation about, say, a particular book and been tempted to say you’ve read it even though you haven’t?

I am guessing the answer is yes. But why would anyone bother to lie in such a low-stakes situation?

The book lie is what you might call a lie of reputation: you are concerned with what other people think of you. Of the many reasons that people lie, I have always thought that the lie of reputation is the most interesting — as opposed to a lie to gain advantage, to avoid trouble, to get out of an obligation, etc.

A new paper by the economists Cesar Martinelli and Susan W. Parker offers some fascinating insights into lies of reputation. It is called “Deception and Misreporting in a Social Program,” and will be published soon in the Journal of the European Economics Association.

Martinelli is a Peruvian-born, U.C.L.A.-educated economic theorist who teaches at I.T.A.M. in Mexico City; Parker is an American-born economist, educated at Yale, who also teaches in Mexico City, at C.I.D.E..

Their paper takes advantage of a remarkably rich data set from Oportunidades, a Mexican welfare program. It records the household goods that people say they have when they are applying for the program and then it also records the household goods that are actually found to be in that household once the recipient’s application has been accepted. Martinelli and Parker worked with data from more than 100,000 applicants, representing 10 percent of the applicants interviewed that year (2002).

It turned out that a lot of people underreported certain items that they thought might exclude them from getting benefits. Below is a list of underreported items followed by the percentage of recipients who owned a certain good but who said they didn’t:

Car (83.10 percent)
Truck (81.71)
Video recorder (79.73)
Satellite TV (73.91)
Gas boiler (73.12)
Phone (73.12)
Washing machine (53.46)

That’s not very surprising: you might expect people to lie to gain the advantage of a welfare benefit. But here’s the surprise. Below is a list of household items that were overreported — i.e., which applicants said they had but in fact did not (again, followed by percentages):

Toilet (39.07 percent)
Tap water (31.76)
Gas stove (28.56)
Concrete floor (25.41)
Refrigerator (12.05)

So 4 out of 10 applicants without a toilet said they had one. Why?

Martinelli and Parker chalk it up to embarrassment, plain and simple. People who were desperately poor were also apparently desperate to not admit to a welfare clerk that they lived without a toilet or running water or even a concrete floor. This is one of the most amazing lies of reputation I can imagine.

It should be noted that there is a lot of incentive to lie to get into the Oportunidades program, for the cash benefit equals about 25 percent of the average applicant household’s expenditures. Furthermore, the penalty for underreporting was not very strong: many of the people found to be underreporting goods like satellite TV’s and trucks were were not kicked out of the program. You could argue that the penalty for overreporting, meanwhile, was greater since it might mean being excluded from the program in the first place — which makes the overreporting even more costly.

The Martinelli-Parker paper may have broad implications for not only poverty programs but any kind of project where the data are self-reported. Think about the typical survey on drug use, sexual behavior, personal hygiene, voting preference, environmental behavior, etc.

Here’s what we once wrote, for instance, in an article about the lack of hand hygiene in hospitals:

In one Australian medical study, doctors self-reported their hand-washing rate at 73 percent, whereas when these same doctors were observed, their actual rate was a paltry 9 percent.

We’ve also written about the subjects that online daters are most likely to lie about, and the risky business of election polling — especially when the issue of race is involved.

But as often as we or anyone else writes about the perils of self-reporting, the Martinelli-Parker paper really gives the whole topic a foundation to stand on. Not only does it deliver a surprising insight into why we lie, but it is also a sobering reminder to naturally distrust self-reported data — at least until some scientists enable us to peer into one another’s minds and see what’s really going on there.

I am interested in hearing from readers what kinds of lies you tell, and why.

[Note: I’ll be discussing this topic early tomorrow (Tues.) morning on the new public-radio program The Takeaway.]


I've been curious for many years about why people lie.

I worked for a man who lied about everything; small things, large things and plain old everyday things. If he was speaking he was lying.

Oddly, at first he was very complimentary to me and about me. It took me about 2 years to discover his lies. When I finally confronted him, he told me everything he had ever said to me was a lie, but that now he was telling the truth.

At that point my head exploded.

I'm lying

Since I'm currently self-reporting, I'll say that as a matter of personal affectation and pride, I try not to lie about anything that benefits me because I see that as a weakness. And the more it benefits me, the more reluctant I am to lie, despite the increasing cost of telling the truth. I honestly believe we're all actually selfishly and communally much better off being honest. If no one could or would lie, once we all had a period of a couple of months with constantly hurt feelings and lonely, we'd adjust and then we'd all find a new, probably happier, and definitely much more efficient and reliable state of rest, knowing our role, other's perceptions of us, etc. Better data leads to more informed and probably better decisions. Except for kids or others who I read under-weigh the negative value of most negative consequences.

But outrageous lies that do not benefit me (other than by amusing me) are probably the most funny thing there is, and I try to engage in those frequently. Yelling is the second funniest thing ever, and so anyone who yells lies absolutely cracks me up. I love politics.



I try to avoid lying in spite of the occasional embarrassment, because I prefer that people like me as I am (the true me) rather than that they like someone who is not me.

Forcing myself to say the truth also trains me to say it in a more diplomatic manner: that is, to say it in such a way that the person I am talking to can see through my ambiguous answer but is also free to pretend that they didn't understand it, in case they don't feel up to discussing it.

In addition, admitting to the truth can sometimes open up communication and thus lead to more interesting interaction.

Ms. One More Caveat for the Freakanomics Record

No doubt you wish me to speak on the subject of "science as a vocation for women." It now seems to be true that I have made a mistake- call it somewhat of a lie, if you will, to myself. But to reveal the truth would be im-modest which is something we women have difficulty with- so for a change- since this is somewhat of a private conversations among friends, I will tell the truth- the greatest real thinker of post-modern times is-- well-- truly yours- in the sense in which I stand as a dwarf upon all of you real and real possible giants who made my own achievement possible!

Signed- Dwarf


I've read Freakonomics


When I lived in a state where petition-initiated, ballot-approved legislation was common, I invariably told petition people that I was not registered to vote.

And when one of them countered that by referring me to a nearby voter registration table, I told her I was a convicted felon.


Let sleeping dogs lie.

Kyle Bradley

RE:Jeane's Comment.
To say that you are not on the electorate, evasively to a candidate, is endemic of the systematic breakdown of the values that the UK have held in high regard for many years. How can political democracy prevail if as a nation we are to apathetic to respond to a candidate who may well run our respective states?


when I went to India strangers kept asking me where I came from ("Austria") and what job I had ("Consultant in the Corporate Treasury field").

I have to commit that after having explained my job 3 times (several minutes for each explanation) I switched to "I work in a bank" and saved me and the people there a lot of unnecessary and uninteresting conversation.


on the male height thing, apparently men under 6ft typically add, on average, 1 inch to height, but guys over 6ft typically add 2 inches, as there is less chance of being caught out.


I was thinking I would like to write an essay on lying myself for the last few years because unlike the lighthearted attitude in most of these comments,I see that lying has become almost immersed into our genome and is already having a detrimental effect on society. There are a million examples lying : Enron, NY former governor, Guantanamo, a million etcs.

By lying just about ordinary things because a. you don't want to face reality and want the "easy way" out, b. you don't want the aggravation of people's responses, c. you don't want to hurt people's feelings, d. you don't want to accept blame for something you were responsible for; it then becomes an attitude in important issues in your work, relationships and society and basically you become a cheater.

I have been living in Egypt for 11 years working on a significant project that is changing the course of healthcare in the developing world. What I discovered early on was that lying is an art form here and seems to be genetically inherited from the Pharaohs, ha, ha. Seriously, I noticed that because lying is so common; it has a significantly detrimental effect on what reality is to people and as result there is enormous difficulty to improve or change anything. If you are not accountable and deny that there is anything wrong you are telling lies that are ultimately detrimental to society and therefore make things that much harder to change.

This is the biggest battle we have fought to make a change because people are lying to themselves and others about what reality is. This is also the biggest battle you are having in America because so many leaders and public are lying about the reality of what is really happening in your country regarding poverty, education, civil rights, healthcare as well as the image that it has on the world stage. This will be a disaster not only for you as America but also for the rest of the world who have seen America as the champion of what is right and true.



Might some of the over-reporting be due to confusion about definitions, rather than lying? For example, if a family shares a toilet with their neighbours, they might answer yes, they have a toilet; but the official survey might conclude that they don't have a toilet (of their own).


Oh man, that came out wrong! (#37) I didnt mean to talk down to Mexicans, I apologize.

I just happen to have Mexico as a reference, we all know this happens everywhere, it is just that in some cultures it happens more than others..

Very interesting subject tho..


Oh man, you are taking on a very interesting subject.
Most people in Mexican culture, do this all the time (to really annoying levels) and the sad part is they DON?T even realize the extent of the cultural implications of this behaviour!

Families, companies, institutions and whole society
structures depend on honnesty and low rates of self deception to succeed!

The worst lies are those we tell ourselves, I mean when we fail to do what we feel we should do.

Every last one of us knows the diference between right and wrong, it is self deception what keeps us from doing it.

I try not to lie, because I hate the feeling of it.

Big Rob

Lpetrie#140 - "more men"? I don't sleep with any men - don't intend to start either - I'm happy if I can sleep with any women in this crazy uptight town. But occasionally I do get "lucky" and get to enjoy the female embrace - if I can stomach the lies - which definitely come with the territory - generally speaking. Even my dear sainted mother lies to me. What gets me is not so much the mendacity as it is the ease and the consciencelessness in which it is nested.

If I lie it is because I get paid to - and I need to earn a living - but the affect of my lie is of beneficicence to almost all: "yes I can do the job!" - so it's a "white" lie - not an: I'll call you tomorrow" lie which is as pointless as it is gratuitous. It's a way of exerting a poor persons vision of power I think. Pitiful, pathetic and perverse.


I lie sometimes not to hurt the sentiments of others


As I was thinking of what lies I've told, I realized I was perfectly willing to admit them in this anonymous form but obviously have more of a problem doing so in real life (otherwise, I wouldn't have lied\fibbed in the first place)

Where any of these surveys completely online, or was there some human-to-human interaction along the way, like over the phone, handing in the application in person, etc. I suspect it makes a difference.

On the question of lying, I just realized that most of the examples I am thinking of make me look good, e.g. lying to protect someone's feelings. Hmmm...

patrick m

I was wondering about your thoughts on the oh-so new york fake-it-till-you-make-it-ness? if, as the philosophical sticker magnets say: -life is about creating yourself, not just finding yourself- is there a creative zone in lying that, akin to positive thinking, could perhaps leave one lying in the lap of luxury, if it's not by such a bad set of lies that would land one in jail?
is there room to talk about lying and 'authentic living' in this context?

patrick meagher

hmm, but what about the so called white lies told in the maintaining or establishing of 'cred' as a part of bonding amongst peers. eg many people will say they heard of something, lets say, like a band, without hearing the music, but then will look it up later, thereby somewhat quasi absolving their lie, while preserving what matters more- a sense of kinship and sharing. this isn't just a hipster thing i imagine, so what's your take on that, and have you heard of this awesome new band called psych? btw, pysch, i made it up, (i think)!


Lies about books might depend on the kind of book. If your boss is raving about the fish market book or seven habits or whatever, you might be tempted to talk it up, and to have a decent chance of doing so in general terms, just from what you've overheard. You'd be rather less likely to do the same thing for, say, _Silas Marner_ or _Jude the Obscure_.

As for the weight on my driver's license: I wrote down the accurate answer, and the person keying it in didn't type it in correctly. The result is that the State of California believes my weight to be approximately what it was when I was twelve years old.