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Latticework of Mental Models: Law of Diminishing Marginal Utility

“Chocolates!” replied Soham, my nephew, with a glint in his eyes. That was his response to my question “What is happiness?”

“So you think the secret of happiness lies in chocolates?” I quizzed him further.

“Yeah! It’s bliss,” he blurted while going around in circles in his tricycle.

“Bliss?” I thought to myself, “That’s quite a mouthful of adjective coming from a five year old.”

“Okay! Here is a chocolate. Tell me if it makes you happy?”

“Thanks Mamaji (that’s what he calls me),” he screamed as he literally snatched it from my hand and in no time the chocolate was gone. He was ecstatic. May be he was right. Chocolate is bliss.

“So if one chocolate makes your happy, more chocolates should make you more happy. Isn’t it?” I was attempting to play Socratic Solitaire (the tradition of asking question that helps somebody discover the wisdom) with an unsuspecting kid.

“Yes…more bliss!” he quipped, while making bigger circles with his tricycle and relishing the after taste of the first eclair. Where in the world did he learn this word ‘bliss’, I wondered.

“All right. So here is another chocolate and let me know if this one makes you more happy than the first one?”

With this move, I thought I was just a few steps away to make the kid realize the futility of materialism. However, what the smart alec inside me didn’t know that in next few minutes, that little boy was going to stump me with his raw intellect.

“Very happy!” he screamed again and gulped the second eclair too.

After two more chocolates, as I expected, Soham’s excitement for the chocolates dwindled and he didn’t look interested in the fifth chocolate.

I started telling him, “So you see, you don’t want the fifth one as much as you wanted the first chocolate. It means happiness is not in chocolates.”

I expected a blank stare from him followed by the expression where the truth dawns upon him. Instead what he said left me dumbfounded.

“No. It’s not in all chocolates. Happiness is in the first four chocolates,” and he took off in his super bike leaving me with my chocolates and the seed for a remarkable insight.

The insight, of course, was about an important mental model from the field of economics. It’s called the Law of Diminishing Marginal Utility.

For the rest of this post, we will use the acronym DMU because it saves screen space, computer memory, internet congestion, and my keyboard strokes. 😉

Let me define DMU now. As a person increases consumption of a product – while keeping consumption of other products constant – there is a decline in the marginal utility that the person derives from consuming each additional unit of that product.

In other words, for each additional unit of a good (in my nephew’s case, a piece of chocolate) the added satisfaction you receive from consuming the good decreases.

Let’s deconstruct it and look at each term in isolation first. What does the term “utility” mean?

In economics, scientists are concerned with examining issues of the supply and demand of goods and services. This theory assumes that people are perfectly rational and make choices about purchasing goods or services depending on what is in their best self-interest.

And how do you measure what is in someone’s best self-interest? This is where the concept of utility comes in. Think of utility as the benefit a person gets from consuming a good or service. For Soham, utility was the satisfaction he gained from eating chocolates.

Now imagine how utility changes (increases or decreases) as a person consumes more of the same good. In Soham’s case, the utility was the highest for the first piece of chocolate. Even the second and third chocolates delivered the same utility as the first one. However, the satisfaction he got from the fourth piece was definitely not as high as the first three. As a result, he refused the offer for the fifth chocolate.

It is important to understand that the concept of utility is a relative one. As a kid, I probably had a higher threshold than Soham and would have accepted half a dozen more eclairs. Different people gain different levels of satisfaction from eating chocolate depending on their preferences.

My friend, Jana has penned a useful post on this concept using the example of pizza consumption.

Let’s explore some areas where DMU surfaces in the world around us.

DMU and Buffet (not Warren!)
I am sure you must have been to one of those “all you can eat” food buffet restaurants offering wide array of food items. Have you wondered how do they manage to provide you so much quantity and variety for such reasonable prices?

Buffet restaurant owners would not make the promise of unlimited food if they weren’t going to make a profit. The simple truth is, they know a secret. And the secret is that we can’t eat all.

Why? DMU, buddy!

Restaurant owners know all too well that each additional plate of food provides less utility than the plate before. By the time we get to our second or third serving, we’re so full that eating anything extra will actually harm us (dis-utility). So, in reality, there is no such thing as all you can eat because we simply cannot eat it all.

By the way, did you know that Coca Cola’s (yes, that caffeinated, celebrity promoted, black coloured sugar syrup) flavour is designed in such a way that it leaves very little aftertaste in your mouth, which means your marginal utility of coke consumption doesn’t diminish as rapidly as it should with any other sugared drink. That is, unfortunately though, the beauty of Coca Cola’s product.

Let’s talk about something other than food.

DMU and Taxes
Benjamin Franklin once said –

In this world nothing can be said to be certain, except death and taxes.

I don’t know about death (haven’t experienced it yet) but there is an interesting rationale behind progressive tax rates. Progressive taxation results when the rate of taxation increases with an increase in income. The logic is based on the assumption that the rich have lower marginal utility of money as compared to the poor people. Hence the rich should be taxed higher.

Loss aversion and DMU
Once you get a hang of DMU, it’s easy to understand Daniel Kahneman’s loss aversion theory which states that losses hurt more than gains feel good. Simply put, the pain generated by a loss of Rs 100 would be more than the pleasure of gaining Rs 100.

This explains why people’s fear of loss is much greater than desire to gain.

Look at the graph above. It shows how the utility goes down with every incremental step. To summarize the graph, if Rs 100 is added to your wallet which already contains two hundred rupees, it gives you a pleasure worth of 15 units. Another hundred, and your pleasure increases by a relatively smaller amount, i.e., 10 units. And so on.

When somebody moves from point B to point A, the utility derived by getting Rs 100 is 15 units. Whereas when one moves from point A to point C, 10 units of utility is derived by gaining Rs 100.

In the same graph, if we start from point A and move towards point B, loss of Rs 100 sets us back by 15 units of utility. On the contrary, if we move from point A to point C, a gain of Rs 100 fetches us a utility of 10 units. So the loss of Rs 100 is heavier, in terms of utility, than a gain of Rs 100. That proves the loss aversion theory. (please see the update on this at end of this post)

DMU in Business and Investing
The concept of marginal utility is also useful in thinking about the idea of marginal cost in businesses. Marginal cost is the cost of producing one more unit of a good. In general terms, marginal cost at each level of production includes any additional costs required to produce the next unit.

For a business which sells software products, the marginal cost of an extra piece of end product is close to zero. However, for a typical brick and mortar business, selling tangible products like FMCG, the marginal cost of additional product is significant.

Consider social networks like Facebook, Twitter or Linkedin. The marginal cost of signing up one additional member is close to zero. But each new member brings non-zero, sometimes pretty substantial, value to the entire network. In general, marginal cost favors businesses that have differentiated products and brand names.

So, extending the above logic, if a manufacturer wants to make a decision about producing more, it should keep producing unless the per unit revenue is less than the marginal cost of production (assuming that all products can be sold). However, this strategy can be fatal for commodity type of business, where every competitor cuts prices so that the price hovers just above the marginal cost.

Airlines is a great example of being victim of marginal cost. So much so that, Charlie Munger calls them ‘marginal cost with wings’.

Many researches have proven that DMU is applicable in case of portfolio construction also. Having multiple stocks in your portfolio decreases the risk of permanent capital loss. However, every additional stock in your portfolio brings down the risk in diminishing order. So much so that, after certain point (many expert suggest that number to be 20), the risk doesn’t decrease at all by adding more stocks.

Increasing Marginal Utility
Your knowledge about an idea, or mental model, isn’t complete until you know where it fails to work. What’s more important, than an idea itself, is the knowledge about its limitations.

Charlie Munger said –

I never allow myself to have an opinion on anything that I don’t know the other side’s argument better than they do.

So let’s see where DMU doesn’t work. Many a times the marginal utility or the marginal cost remains constant with additional unit of consumption. Can you think of an example?

If you buy 1 kg of gold bar for x rupees, how much would you have to spend for 2 kg of gold? 2x. And the equation is linear. No DMU here!

Can you think of an example where the marginal utility not just stays constant but increases with each additional unit of consumption? Some of you might be tempted to say “alcohol”. Well, I like the way you think but I am calling it a dry day today. 😉

Diamond! The price of a 10 carat diamond is not twice the price of a 5 carat diamond. In fact, the price for every additional carat increases pretty rapidly and non-linearly.

“Anshul, can we please talk about something other than jewelry and Jack Daniels?” I hear your concerns. Okay, how about stock market?

In stock market, when somebody wants to buy a meaningful stake in a company, perhaps with an intention of acquiring control, the marginal utility of every additional share and its cost increases. That’s why most of the acquisitions happen at a large premium to the current market price.

We can call this phenomenon as the law of increasing marginal utility. I am not sure if this term is recognized by economists so lets just keep it between you and me.

Oh, I almost forgot to mention. The pleasure I derive out of writing this Latticework series – that follows the law of increasing marginal utility for me. How about you? I hope it’s not DMU for you.

What we learnt today is that people aggressively place a lower value to each additional unit of something that they get in increasing abundance.

I am sure you can spot many other use cases where this mental model applies. I would be glad to hear from you.

We’ve had some great insights shared by our tribe members in previous posts. Let’s not lose the momentum. I urge you to keep the ball rolling. Let it become a snowball. A snowball of learning and worldly wisdom.

Take care and keep learning.

Update: One of the tribe members pointed out an error in my attempt to explain DMU and Prospect Theory using the same graph. Please read the snippet of the email exchange here

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About the Author

Anshul Khare worked for 12+ years as a Software Architect. He is an avid learner and enjoys reading about human behaviour and multidisciplinary thinking. You can connect with Anshul on Twitter.


  1. Nice article Anshul. DMU is indeed a powerful concept we all experience in one form or another. I had done a post on this: ‘What eating pizza can teach us about wealth building’

    Knowing that increased consumption is often not worth what we pay since our costs are linear while enjoyment (utility) is a flattening curve, enables us to question spending decisions.

  2. Vikas Gupta says:

    Another Gem from anshul 🙂 Thanks for the post.

    (Due to reciprocity syndrome 😛 ) I think additional information/data while taking decisions can also cause DMU.

    For example, while buying a car/ketchup/clothes etc, where if incase you are given 50 choices, the fun of buying keeps on getting reduced due to tremendous amount of work load on the decision maker due to so many choices and differences to calculate.

    The same can be said about any purchase decision , in which the buyer does not know the nuances of the product, and gets bombarded with options, which leads him to think “I just want to get done with this work asap”.
    (Real estate, selecting location for vacation, buying laptop/desktop, LCD etc etc) I can say for myself, its kind of getting lost in the labyrinth when I go to lamington road, to buy computer peripherals for assembling a desktop. 😛

    I dont know if I am correct with the above example 🙂

  3. Vikas Gupta says:

    Sorry Anshul for posting 2nd comment, I got a “ah ha” moment just now.

    To simplify the above, I think we could say that :- When a person doesn’t know much about the field/product/sector, for which he has to take a decision and the situation is presented with lots of options and choices, any additional data would result in DMU.

    “BUT” in the same situation , a person who is expert or has knowledge about the product nuances can use and make any additional information in to an advantage. I.e for such person , its Law of increasing marginal utility.

    What do you think about the above?

    • Precisely what Malcolm Gladwell says in the book Blink. Read it, its one heck of a book.

    • Anshul Khare says:

      Hey Vikas,

      Thanks for sharing your insights. They make a lot of sense. Let me extend your argument for investment research process also.

      When somebody starts researching a stock and collects information about the business/company/industry, 80 percent of the most important information is gathered in initial 20 percent of the time invested. Any additional time after than fetches diminishing marginal information.

      However, as you pointed out, even a small piece of newly available information could be very crucial but you need expert eyes and high competence in that area to differentiate the signal from noise.

      I would like to quote John Maynard Keynes here, who said – “When the facts change, I change my mind. What do you do sir?”

      But there is a catch. Statistics have repeatedly shown that majority of the additional new information is noise. So one strategy to deal with this paradox is – avoid the instant consumption of constant inflow of new information and look at the data in batches, e.g. evaluating the health of a business every 6 months instead of watching the news every day.

      Hope that helps.


  4. Fantastic article! Alongside death and taxes, I would like to add MONEY as well. The more one has it, the more he wishes to have.

    • Anshul Khare says:

      Thanks Sumit!

      As far as money is concerned, it’s subjective I believe.

      For some people money does follow a DMU pattern. And for others it could be the reverse. So money probably is neutral.

      That’s entirely my personal view and I could be wrong. 🙂

  5. Vicky Rathod says:

    Marginal Utility for reading increases after reading every article of safalniveshak 🙂

  6. Srikanth Thunga says:

    How does DMU work when you give 1 chocolate to your nephew at 9a everyday?

    • Anshul Khare says:

      Haven’t tried that Srikanth but that’s a very interesting thought!

      On further reading (thanks for sharing the link), I learnt that one of the assumptions of DMU is that the time gap between consumption of units (chocolates) shouldn’t be too high. So for DMU to be valid the so called after taste (satiation produced by consumption) shouldn’t dwindle to zero before consuming the next unit.

      So the Coca Cola’s example is useful here because having few cokes with in few minutes is as good as having them on different days (in terms of utility derived)

      This reminds me of a related insight that Daniel Kahneman shared in his book Thinking, Fast and Slow. It says that to maximize happiness, we should spread out the pleasurable tasks over longer periods and concentrate the unpleasant tasks together.

      So if Soham had 10 chocolates, his overall happiness (or bliss in his words) would be highest if he eats one chocolate everyday. And if he has to perform unpleasant tasks like finishing his homework, it’s better that he finishes it in one go rather than doing it bit by bit every few hours. That would minimize his long term unhappiness.

      I couldn’t help but think about Steve Jobs here because the insight correlates pretty well with his advice. Why delay enjoying till retirement? That’s like bunching all the pleasurable activities together to be experienced for a shorter duration (retirement time). It’s better to spread those pleasurable activities (doing the work that you love) across your whole life, starting now. Little life philosophy here but connects well with DMU 🙂


  7. Anshul,

    Excellent post as usual. For some reason money doesn’t follow the rules of DMU and I don’t know why. Take a look at the excellent video which Prof. Bakshi tweeted to emphasize this point:


    • Anshul Khare says:

      Thanks Jana! 🙂

      I guess that’s what separates the greed from rationality. For somebody the after taste of a million may last for a long time and for others it may just be over in a minute, so much so that they don’t even know how much more will satiate their appetite.

  8. R K Chandrashekar says:

    Dear Anshul & Vishal
    This law doesn’t apply to Safal Niveshak-right from day one! Again as some have pointed out, so to with wealth-money variety, not for all, but far to many!! Again the joy in making the 1st million reduces when you move to the 2nd million.
    Now on a lighter note; if you had tried the chocolate experiment on me, you would have burned your fingers; and if you had asked my family where this rule doesn’t apply- they will point to me with delight and dismay. Given my age and with a proactive lawyer daughter, I am consciously trying to reduce.
    By the way, I have a tooth extraction lined up for the day- not the sweet tooth!! Cheers

    • Anshul Khare says:

      Thanks Mr. Chandrashekar!

      Great to know that you love chocolates. I’ll bring a bigger pack when we meet. 😉


  1. […] who is known for his pioneering work in the field of behavioural economics, came up with the Loss Aversion theory, which explains the root of many of the human psychological biases. The theory says that human […]

  2. […] or something to compare with to assess the value of something. Using this insight let’s see what The Law of Diminishing Marginal Utility says […]

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