Principles of Finance Lecture 5: Utility Theory
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Questions and Answers

What is the end-of-period wealth for investment 1 if the investor gains $10?

The end-of-period wealth for investment 1 would be $2010.

What is the expected utility for investment 2 given its probabilities and outcomes?

The expected utility for investment 2 is approximately 7.601.

What is the Pratt-Arrow risk premium for investment 1?

The Pratt-Arrow risk premium for investment 1 is $0.

Calculate the expected wealth for investment 2 considering the probabilities and outcomes.

<p>The expected wealth for investment 2 is $1750.</p> Signup and view all the answers

What key difference exists between the Pratt-Arrow risk premium and Markowitz's risk premium?

<p>The Pratt-Arrow risk premium focuses on utility while the Markowitz risk premium considers mean and variance.</p> Signup and view all the answers

What is the variance of end-of-period wealth used for in investor choice theory?

<p>The variance of end-of-period wealth is used to measure the risk associated with investment outcomes.</p> Signup and view all the answers

What does the term 'stochastic dominance' refer to in investor choice theory?

<p>Stochastic dominance refers to a situation where one investment is preferred over another under uncertainty.</p> Signup and view all the answers

How does the normality assumption simplify decision-making for investors?

<p>The normality assumption simplifies decision-making by allowing the use of mean and variance for investment analysis.</p> Signup and view all the answers

What is the formula for the Pratt-Arrow measure of a local risk premium?

<p>The formula is $π = \frac{σ_{Z}^2}{2}U''(W) - U(W)$.</p> Signup and view all the answers

Define Absolute Risk Aversion (ARA).

<p>ARA is defined as $ARA = -\frac{U''(W)}{U'(W)}$.</p> Signup and view all the answers

What does Relative Risk Aversion (RRA) measure?

<p>RRA measures the level of risk aversion relative to wealth, defined as $RRA = -\frac{U''(W)}{W U'(W)}$.</p> Signup and view all the answers

For a power utility function $U(W) = -W^{-α}$, what can be inferred about ARA and RRA?

<p>Both ARA and RRA are constant in $W$ for power utility functions.</p> Signup and view all the answers

Given the logarithmic utility function $U(W) = \ln(W)$, how do ARA and RRA behave?

<p>ARA decreases and RRA is constant as $W$ increases.</p> Signup and view all the answers

What does the expected utility formula represent in terms of wealth?

<p>It represents the expected wealth at the end of a period, considering the risk profile of the investor.</p> Signup and view all the answers

How do utility functions differ among individuals?

<p>Utility functions are specific to individuals but changes in marginal utility can be compared across them.</p> Signup and view all the answers

Explain how uncertainty impacts rational decision-making in investment.

<p>Uncertainty requires investors to assess risk, influencing their choice based on expected utility.</p> Signup and view all the answers

What is the relationship between the local risk premium and investor choice?

<p>The local risk premium affects how investors value risky assets and their willingness to take on risk.</p> Signup and view all the answers

Define a risk-averse investor.

<p>A risk-averse investor dislikes risk and seeks compensation for taking it.</p> Signup and view all the answers

What role does the uncertainty of returns play in the investor's judgment?

<p>Uncertainty of returns compels investors to evaluate potential risks versus returns in their decisions.</p> Signup and view all the answers

What is characteristic of a risk-neutral investor's decision-making process?

<p>A risk-neutral investor makes decisions solely based on expected end-of-period wealth, ignoring risk.</p> Signup and view all the answers

What motivates a risk lover in investing?

<p>A risk lover enjoys taking risks and seeks compensation for avoiding risk.</p> Signup and view all the answers

How can we express the expected utility of end-of-period wealth mathematically?

<p>The expected utility can be expressed as $E[U(W)] = \sum_{i} p_i U(W_i)$, where $p_i$ is the probability of wealth $W_i$.</p> Signup and view all the answers

In the context of a fair gamble, what factors influence an investor's decision to invest or not?

<p>An investor's initial wealth and their risk profile significantly influence the decision to invest.</p> Signup and view all the answers

What is the role of risk attitude in rational decision making under uncertainty?

<p>Risk attitude determines how an individual evaluates potential decisions amidst uncertainty, influencing their choices.</p> Signup and view all the answers

How does a risk-averse investor typically respond to uncertain outcomes?

<p>A risk-averse investor prefers to avoid risk and will often choose a guaranteed outcome over uncertain potential gains.</p> Signup and view all the answers

What is meant by 'certainty equivalent wealth' in investment choices?

<p>Certainty equivalent wealth refers to the guaranteed amount of wealth an investor would accept instead of taking a risk with uncertain outcomes.</p> Signup and view all the answers

What characterizes a risk-loving investor's utility function?

<p>A risk-loving investor has a convex utility function, indicating they derive higher utility from risky choices compared to certain outcomes.</p> Signup and view all the answers

How does the expected utility differ for a risk-neutral investor?

<p>For a risk-neutral investor, the expected utility equals the utility of the expected wealth, as their utility function is linear.</p> Signup and view all the answers

What does the risk premium represent in investment decisions?

<p>The risk premium represents the difference between the expected wealth and the certainty equivalent wealth.</p> Signup and view all the answers

In the provided investment scenario, what does it mean when expected end-of-period wealth is equal for both alternatives?

<p>It means that, on average, both investment options provide the same amount of wealth at the end of the period, but not necessarily the same level of utility.</p> Signup and view all the answers

What is the relationship between expected wealth and utility for risk-averse investors?

<p>Risk-averse investors typically find that the expected utility of a certain outcome is greater than the utility of expected wealth, indicating they value certainty more.</p> Signup and view all the answers

Describe how attitudes towards risk can influence investment choices.

<p>Attitudes towards risk can significantly affect investment choices, with risk-averse investors favoring safer options, while risk-tolerant investors may seek higher returns through riskier investments.</p> Signup and view all the answers

In the context of normally distributed random variables, what two parameters fully describe a normal distribution?

<p>The mean and variance.</p> Signup and view all the answers

How is the expected return $R̄$ defined in terms of asset returns?

<p>It is defined as $E(R) = rac{E(W_f) - W_0}{W_0}$.</p> Signup and view all the answers

What is the relationship between end-of-period wealth and returns under the normality assumption?

<p>Returns, $R$, can be expressed as $R = rac{W_f - W_0}{W_0}$, where $W_f$ is the end-of-period wealth.</p> Signup and view all the answers

What does the variance of returns, $ heta_R^2$, represent?

<p>It represents the variability or risk of asset returns.</p> Signup and view all the answers

What does it mean when we say returns are normally distributed, denoted as $R ∼ N(R̄, heta_R^2)$?

<p>It means that returns follow a normal distribution characterized by mean $R̄$ and variance $ heta_R^2$.</p> Signup and view all the answers

Explain the implication of rational decision-making based solely on mean and variance in investment contexts.

<p>It implies that investors make decisions based on expected return and risk, ignoring other factors.</p> Signup and view all the answers

What formula represents the calculation for the variance of returns using end-of-period wealth?

<p>The variance of returns is calculated as $ heta_R^2 = E[(R - E(R))^2]$.</p> Signup and view all the answers

In the equation for expected return, what does $W_0$ represent?

<p>It represents the initial wealth at the beginning of the investment period.</p> Signup and view all the answers

What significance does the mean, $ar{W}$, hold in investment decision-making?

<p>The mean represents the average expected wealth at the end of the investment horizon.</p> Signup and view all the answers

How do you express the variance of wealth, $ heta_W^2$, in terms of expected wealth?

<p>It can be expressed as $ heta_W^2 = E[W_f^2] - (E[W_f])^2$.</p> Signup and view all the answers

What are the two key definitions of risk aversion introduced by Pratt and Arrow?

<p>Absolute risk aversion and relative risk aversion.</p> Signup and view all the answers

If an investor's utility function is defined as U(W) = W^2, how would they generally respond to a risky investment?

<p>They would likely avoid the investment due to risk aversion, preferring safer options.</p> Signup and view all the answers

What does the expected utility theory suggest about the relationship between risk and utility?

<p>It suggests that individuals choose investments to maximize their expected utility, often leading to risk aversion.</p> Signup and view all the answers

How is the certainty equivalent (CE) calculated in the context of risky investments?

<p>CE is calculated as CE = E(W + Z) - π(W, Z), where π is the risk premium.</p> Signup and view all the answers

Explain the significance of the risk premium in relation to end-of-period wealth.

<p>The risk premium represents the amount above the expected value of a gamble that an investor requires to accept the risk.</p> Signup and view all the answers

What are the implications of an actuarially neutral gamble on the expected wealth of an investor?

<p>An actuarially neutral gamble has an expected value of zero, meaning it neither adds nor subtracts from expected wealth.</p> Signup and view all the answers

In the context of risk aversion, what does a utility function of U(W) = ln(W) indicate?

<p>It indicates decreasing marginal utility, implying that as wealth increases, the additional satisfaction from each extra dollar decreases.</p> Signup and view all the answers

Describe how Taylor series expansion is used in the context of investment utility functions.

<p>Taylor series expansion approximates the utility of wealth by taking into account the variance and higher moments of the utility function.</p> Signup and view all the answers

What is the expected value of a gamble with outcomes z1 and z2 with probabilities p1 = p2 = 0.5 when E(z1 + z2) = 0?

<p>The expected value is zero, as the outcomes balance each other out.</p> Signup and view all the answers

How does the level of risk aversion affect investment decisions?

<p>Higher levels of risk aversion lead to more conservative investment choices, favoring lower-risk options.</p> Signup and view all the answers

Study Notes

Principles of Finance - Lecture 5: Utility Theory Under Uncertainty

  • Utility theory under uncertainty is a rational decision-making framework for situations with unknown future outcomes.
  • Previously, decisions were made under certainty, where market interest rates and investment returns were known.
  • Uncertainty now exists because future market interest rates and subsequent returns are unknown.
  • Today's lecture focuses on the theory of rational decision-making under uncertainty, guiding investor choices among risky alternatives.
  • Key considerations include risk aversion, time preferences, and choice objects.
  • This framework is used to analyze how investors approach and choose actions in uncertain environments.

Axioms of Choice Under Uncertainty

  • Axiom 1: Comparability (completeness): An investor can compare any two investment options. Either one is preferred, the other is preferred, or they are equivalent.
  • Axiom 2: Transitivity: If an investor prefers option X to Y, and Y to Z, then they must prefer X to Z.
  • Axiom 3: Strong Independence: An investor's preferences remain consistent when presented with probabilistic outcomes.
  • Axiom 4: Measurability: Utility of outcomes/choices can be numerically quantified.
  • Axiom 5: Ranking: Investment preferences can be ranked consistently. If all axioms hold, choices are rational and coherent.

Utility Functions

  • Utility functions represent an investor's preferences for risky outcomes.
  • Utility functions are order-preserving, meaning if one outcome is preferred to another, its corresponding utility value is also greater.
  • Utility functions uniquely rank outcomes and can be used to evaluate combinations (expected utility).
  • Expected utility is calculated by weighing the utility of each possible outcome by its probability.

Expected Utility

  • Maximizing expected utility from end-of-period wealth is the goal of a rational investor under uncertainty.
  • The formula for expected utility is
  • E[U(W)] = ΣpᵢU(Wᵢ)
  • where:
    • S is the set of uncertain alternatives,
    • i is a specific alternative,
    • pᵢ is the probability of alternative i,
  • Wᵢ is the wealth for alternative i.

Risk Profiles of Investors

  • Risk Averse: Investors dislike risk and need compensation for taking it.
  • Risk Neutral: Investors are indifferent to risk, considering only expected wealth.
  • Risk Lover: Investors prefer risk and need compensation for avoiding it.

Certainty Equivalent Wealth and Risk Premium

  • Certainty equivalent wealth (CE): The level of wealth an investor would accept with certainty.
  • Risk premium (π): The difference between the expected value and the certainty equivalent.
  • π = E(W) - CE
  • This reflects an investor's aversion to uncertainty.

Risk Profile of the Investor

  • Three types of risk profiles exist: risk averse, risk neutral, risk lover, all reflected in an investor's utility function.

Level of Risk Aversion

  • Absolute risk aversion (ARA) and relative risk aversion (RRA), key indicators of investor risk sensitivity.
  • Investors are commonly risk-averse.
  • ARA and RRA are calculated using derivatives of a utility function
  • ARA= U''(W)/U'(W)
  • RRA= -W(U''(W)/U'(W))

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Explore the Utility Theory under uncertainty in this insightful lecture. Understand how rational decision-making applies when future outcomes are unknown, focusing on risk aversion and investor choices. Key axioms guide how choices are made in uncertain environments.

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