पर्सनल फायनान्स - भाग ८ - बिहेवियरल इकॉनॉमिक्स

भाग १...भाग २...भाग ३...भाग ४...भाग ५...भाग ६...भाग ७...

भाषांतराचे काम सुरू आहे. <अपूर्ण>

डॅनियल काहनेमन आणि आमोस ट्वेर्स्की यांनी १९७९ मध्ये प्रॉस्पेक्ट थिअरी मांडली. उपलब्ध पर्यायांपैकी कुठला पर्याय निवडायचा, हा आपला निर्णय नेहमीच रॅशनल (मराठी? - तत्वतः अचूक?) नसतो, तर ते पर्याय आपल्यासमोर कसे मांडले आहेत, त्यानुसार आपण तो निर्णय घेतो, असे त्यांचे म्हणणे होते.

Earlier, psychophysical theory suggested that if you want to study the subjective value of wealth, you should ask direct questions about wealth, not about changes in wealth. However, later, Harry Markowitz proposed a theory in which utilities were attached to changes of wealth rather than states of wealth.

पुढील उदाहरण बघू:
तुम्ही पुढील २ पर्यायातून दर वेळी काय निवडाल?
प्रश्न १) $९०० हमखास जिंकणार किंवा ९०% शक्यता तुम्ही $१००० जिंकणार?
ठरवले का उत्तर....?

प्रश्न २) $९०० हमखास हरणार किंवा ९०% शक्यता तुम्ही $१००० हरणार?
ठरवले का उत्तर....?

थांबा.... विचार करा... उत्तर बघू नका.

In 1) most people would have chosen sure thing. The risk-averse choice would not have surprised Bernoulli. The risk seeking choice in 2) is mirror image of problem 1). The (negative) value of losing $900 is much more than 90% of the (negative) value of losing $1000. In this case, people however prefer to gamble. Kahneman & Tversky noticed that people become risk seeking when all their options are bad. They also noticed that people had different attitudes to risk for gains and losses.

आता पुढील प्रश्न बघा:
प्रश्न ३) तुमच्याकडे जे काही पैसे आहेत, त्याशिवाय तुम्हाला $१००० दिले
मग तुम्हाला सांगितले की पुढीलपैकी १ पर्याय निवडा.
५०% शक्यता तुम्ही $१००० जिंकणार किंवा $५०० हमखास जिंकणार
ठरवले का उत्तर....?

प्रश्न ४) तुमच्याकडे जे काही पैसे आहेत, त्याशिवाय तुम्हाला २००० रुपये दिले
मग तुम्हाला सांगितले की पुढीलपैकी १ पर्याय निवडा.
५०% शक्यता तुम्ही $१००० हरणार किंवा $५०० हमखास हरणार
ठरवले का उत्तर....?

थांबा.... विचार करा... उत्तर बघू नका.

पहिल्या प्रश्नात बहुतेकांनी सांगितले की ते हमखास मिळणारे $५०० निवडतील.
दुसर्‍या प्रश्नात बहुतेकांनी सांगितले की ते "५०% शक्यता तुम्ही $१००० हरणार" ही शक्यता निवडतील. म्हणजेच ते ५०% चान्स घ्यायला तयार होते.

याचा अर्थ काय? आपल्याला जिंकायला आवडते, हरायला आवडत नाही. - आणि हरणे हे जिंकण्यापेक्षा अजून आवडत नाही.

Prospect theory contends that people value gains and losses differently, and, as such, will base decisions on perceived gains rather than perceived losses. Thus, if a person were given two equal choices, one expressed in terms of possible gains and the other in possible losses, people would choose the former - even when they achieve the same economic end result.

According to prospect theory, losses have more emotional impact than an equivalent amount of gains.

In Bernoulli's theory you need to know only the state of wealth to determine its utility. But in Prospect theory, you also need to know the reference state. Prospect theory is therefore more complex than utility theory.

The graph shows psychological value of gains and losses which are "carriers" of value in Prospect theory (unlike Bernoulli's theory in which states of wealth are carriers of value).

It is S shaped curve which represents diminishing sensitivity for both gains and losses.

Finally, the two curves of S shape are not symmetrical. The slope of the function changes abruptly at the reference point: the response to losses is stronger than response to corresponding gain. This is loss aversion.

- The usual reference point is the status quo, but it can also be the outcome that you expect or the outcome for which you feel entitled for example: the raise or bonus that your colleagues receive. Outcomes that are better than reference point are gains. Below the reference point they are losses.

- Subjective difference between $900 and $1000 is much smaller than the difference between $100 and $200

- The third principle is loss aversion. Losses loom larger than gains.This asymmetry has evolutionary history. Organisms that treat threat have a better chance to survive and reproduce. But remember that many times you have the option NOT to accept the gamble.

Loss aversion:

Many of the options we face in life are "mixed": there is a risk of loss and an opportunity for gain and we must decide whether to accept the gamble or reject it.

Problem 5) You are offered a gamble on the toss of a coin.

If the coin shows tails, you lose $100

If the coin shows heads, you win $150

Is this attractive? Would you accept it?

To make the choice, you must balance "psychological benefit" of getting $150 against psychological cost of losing $100. Although, the expected value of gamble is positive, you may reject it. Fear of losing $100 is more intense than hope of gaining $150

To measure the extent of your aversion, ask yourself a question. What is the smallest gain I need to balance an equal chance to lose $100? For many people, the answer is $200, twice as much as the loss. The "loss aversion ratio" has been estimated in several experiments is usually in the range of 1.5 to 2.5 This is average and may vary. Risk takers in financial market are more tolerant of losses, probably because they do not respond emotionally to every fluctuation.

This theory also explains following 2 things:

- In mixed gambles, where both a gain and a loss is possible, loss aversion causes extremely risk-averse choices.

- In bad choices, where a sure loss is compared to a larger loss that is merely probable, diminishing sensitivity causes risk seeking.

Limitations of Prospect theory:

- Prospect theory cannot deal with disappointment.

A. one chance in million to win $1 million

B. 90% chance to win $12 and 10% chance to win nothing

C. 90% chance to win $1 million and 10% chance to win nothing

Winning nothing is possible in all 3 gambles and prospect theory assigns "same" value to that outcome. Winning nothing is reference point and its value is zero. In first 2 cases, assigning it a zero value makes good sense. But failing to win in third case is considered huge disappointment. High probability of winning the large sum sets up tentative new reference point. (Like a salary that has been promised informally.) Relative to your expectations, winning nothing is considered a huge loss. But Prospect theory cannot deal with disappointment.

- Prospect theory and utility theory fail to allow for regret.

Problem 6) Choose between 90% chance to win $1 million or $50 with certainty

Problem 7) Choose between 90% chance to win $1 million or $150,000 with certainty.

Failing to win is a disappointment in both, but potential pain in problem 7) is compounded. In regret, the experience of outcome depends on an option you could have adopted, but did not.

To conclude:

The complexity of prospect theory was more acceptable in the competition with expected utility theory because it did predict observations that expected utility theory could not. Prospect theory could explain concepts of reference point and loss aversion. It also captures the idea that people tend to overreact to small probability events, but under react to large probabilities. Danial Kahneman won Nobel Prize in Economics for this theory in 2002. Unfortunately, Tversky had died in 1996, so he could not be awarded Nobel Prize.

अपूर्ण