Objective 2 Flashcards
What are 2 approaches to model extreme events?
(FERM12)
- Generalized Extreme Value Distribution
- Generalized Pareto Distribution
Describe the general principle behind the Generalized Extreme Value Distribution
(FERM12)
- It considers the maximum observation (Xm) from each sample (of iid RVs), and pools them together to form an extreme loss data population
- As the size of a sample increases, the distribution of the maximum observation converges to the generaized extreme value (GEV) distribution
What is the cummulative distribution function of the GEV?
(FERM12)
What are 2 methods to take extreme values?
(FERM12)
- Return level approach
- Take the highest obervation in each block of data
- Return period approach
- Set a level above which an observation could be regarded as extreme
- Take the observations higher than the level in each block of data
What is a major drawback of the GEV distribution?
(FERM12)
By using only the largest value(s) in each block of data, it ignores a lot of potentially useful information
Describe the idea behind the Generalized Pareto Distribution
(FERM12)
- G(x) is the distribution of a RV X in excess of a fixed hurdle u given that X is greater than u
- Assume the observations are iid
- As the threhold increases, the distribution of the conditional loss distribution converges to a GPD
What is the cummulative distribution of GPD?
(FERM12)
What is a key consideration when using GPD?
(FERM12)
Choosing the right omega threshold
What are 3 characteristics of financial time series?
(FERM14)
- Serial correlation does not exist to the extent that it is possible to make money from it
- There is strong serial correlation in a series of absolute or squared returns
- The distribution of market returns appears to be leptokurtic (i.e., extreme values tend to occur closely together)
What are 3 characteristics of multivariate return series?
(FERM14)
- Correlations do exist between stocks, and between asset classes and economic variables
- There is little evidence of cross-relation (i.e., change in stock price t has little effect on stock price t+1)
- The time series of extreme returns are individually leptokurtic and they have jointly fat tails
What are the 3 most common ways to measure spread?
(FERM14)
- Nominal Spread
- Static Spread
- Option-Adjusted Spread
What is nominal spread and how is it calculated?
(FERM14)
- The difference between the gross redemption yields of the credit security and the reference bond (e.g., a treasury bond)
- Quick and easy to measure/calculate
NS = rGY - rREF
What is static spread and how is it measured?
(FERM14)
- The addition to the risk-free rate required to value cash flows at the market price of a bond
- It considers the full risk-free term structure and the constant (spread) SC added to the yield at each duration
Bond Price = Sum over t [CashFlowt / (1 + rf,t + SC)]
What is the option adjusted spread and how is it applied to calculate Bond Price?
(FERM14)
- Allows for a large number of stochastically generated interest rates (rf,t,sim) such that the expected yield curve is consistent with that seen in the market
- It considers any options that are present in the credit security (OAS)
How are government bonds’ expected returns estimated?
Both domestic and overseas government bonds are risk-free
Returns are estimated from the gross redemption yield, an annual compound interest rate
What is the difference between corporate bonds and government bonds?
What is credit spread?
(FERM14)
- Corporate bonds are not risk-free and have a chance of default, so their expected returns should consider a risk premium
- Credit spread represents the additional return offered to investors with repect to the credit risk being taken
What are 5 reasons why the credit spreads are higher than historical studies’ findings?
(FERM14)
- Credit risk premium - reward for volatility relative to risk free securities
- Liquidity risk premium - reward for lower liquidity compared to government bonds
- Risk aversion premium - reward for possibility of extreme events and skeyness of bond payoff structure
- Tax premium - less favorable treatment compared to government
- Correlation premium - correlation between credit spreads and interest rates is typically negative
What CAPM and what is the formula behind it?
(FERM14)
Capital Asset Pricing Model
rx = r* + ßx (ru - r*) where
rx = rate of return on individual investment X
r* = risk-free rate of return
ru = market return
ßx = σxpx,u / σu
What are the 6 properties of a good benchmark?
(A good benchmark is important when considering market risk!)
(FERM14)
- Unambiguous (components and constituents should be well-defined)
- Investable (can buy components of a benchmark and track it)
- Measurable (can quantify the vaue of a benchmark with reasonable frequency)
- Appropriate (consistent with investor’s style and objectives)
- Reflective of current investment opinion (contains components about which investor has opinions)
- Specified in advance (known by all participants before the period of assesment)
What is are 8 specific criteria against which a benchmark can be measured in its appropriateness?
(A good benchmark is important when considering market risk!)
(FERM14)
- Proportion (should contain a high proportion of the securities held in the portfolio)
- Turnover (benchmark’s constituents’ turnover should be low)
- Allocations (shoud be investable position sized)
- Position (investor’s active position should be given relative to the benchmark)
- Variability (benchmark variability to the portfolio should be lower than market variability to portfolio)
- Positive correlation between rX - rU and rB -rU
- Zero correlation between rX - r<span>B</span> and rB -rU
- Style exposure (must be similar between portfolio an benchmark)
What is the Black-Scholes Model used for?
What are the formulas?
(FERM14)
Used to model European call and put options
Call = C0 = X0 N(d1) - Ke-r*T N(d2)
Put = P0 = Ke-r*t N(-d2) - X0 N(-d1)
where
d1 = [ln(X0/K) + (r* + σ2X/2)T] / [σX sqrt(T)]
d2 = d1 - σX sqrt(T)
What are two types of interest rates?
(FERM14)
- Spot rates
- (1 + rt)-1 = e-st
- Forward rates
- e-st = e -(f1 + f2 + … + fT)
What is the bootstrapping approach?
(FERM14)
Constructing a spot rate curve from the gross redemption yields on a series of bonds with a range of terms
What are 6 single-factor interest rate models?
(FERM14)
What is the difference between lognormal and normal movements?
(FERM14)
- In lognormal,
- Volatility term is proportional to the interest rate level r
- Interest rates can never be negative
- In normal,
- Volatility term is independent of interest rate level r
- Interest rates can become negative
What are the pros and cons of one-factor interest rate models?
(FERM14)
- Pros
- Works well for simulating a single interest rate, particularly short-term (3M or 1Y) spot rates
- Can be used to simulate the movement of a different sport rate with a longer term
- Cons
- Not good for modeling different points on a yield curve
What are the relevant formulas to calculate modified duration (BDX), bond convexity (BCX), and change in bond price (BPX)?
How is interest rate calculated?
(FERM14)
Interest rate can be solved for in the change in BP formula.
What is the formula for interest rate parity?
(FERM14)
What are the two components of credit risk?
How does it relate to the purposes of modeling credit risk?
(FERM14)
- Probability of default (PD)
- Model how likely the credit event is to occur
- Magnitude of loss given default (LGD)
- Determine the extent of loss that will be incurred
What are 3 factors that affect the credit spread and default risk?
(FERM14)
- Debt seniority (more senior issues have an earlier call on assets remaining)
- Presence of collateral (a collateral lowers level of risk)
- Types of collateral (the more liquid, the better loan ters)
What are 3 broad types of quantitative credit models?
(FERM14)
- Credit scoring
- Uses features of an entity (e.g., financial ratios) to arrive at a score that represents the likelihood of its insolvency
- Examples:
- Probit and logit
- Altman’s Z-score
- k-nearest neighbor approach
- Support vector machines
- Structural form
- Models the value of an entity (e.g., debt value or equity value)
- Examples:
- Merton
- KMV models
- Reduced form
- Uses credit rating to derive a probability of default
What is the general idea behind Probit and Logic models?
(FERM14)
- Regression coefficients can be applied to give a soce representing the probability of default
- They consider numberal characteristics of firms (e.g., financial leverage and income) that have defaulted or remained solvent
- They offer highly effective approaches to determine risk
- But, they do not allow the inclusion of qualitative factors
What is the most familiar discriminant analysis credit modeling approach?
(FERM14)
- Altman’s Z-score
- It gives each firm a score that represent the probability of default:
- Zn > 2.99 : is safe
- 1.80 <= Zn <= 2.99 : uncertain
- Zn < 1.8 : risk of distress
What are the 2 reasons why Z-score uses financial ratios?
(FERM14)
- Ratios allow firms of different sizes to be compared on a consistent basis
- Ratios allow sensible comparisons to be made over time
What is the k-nearest neighbor approach?
(FERM14)
- A non-parametric model that considers the characteristics of a number of firms that fall into one of two groups (solvent or insolvent)
- When a new firm is considered, its distance from a number (k) of neighbors is assessed- the proportion of these neighbors that have become insolvent gives an indication of the likelihood that this firm will also fail
What is the support vector machines (SVMs) approach?
(FERM14)
An approach that uses a line to separate two groups (solvent vs insolvent) of data based on some measures (e.g., leverage, earnings cover)
Visually describe the k-nearest neighbor approach and SMVs
(FERM14)
What is the Merton model?
What is its core assumption?
(FERM14)
- An equity-based approach to model credit risk
- The firm value as a whole follows a lognormal random walk, and insolvency occurs when the firm value falls below the level of debt oustanding
- Pr(XT<=B) = N(-d2)
What is the KMV model?
How is it calculated?
(FERM14)
- It uses the capital structure of the firm to estimate the probability of default, where
- The level of a firm’s debt B is replaced by a B~ = STD + 0.5 LTD
- Values X0 and σX are derived rather than directly observable
- Distance to default is calcualted as:
DD = ( X0 - B~) / (X0 σX)
How do credit migration models work?
(FERM14)
- Uses transition matrices to infer default probabilities, produced by most crediting rating agencies produce these
What is a Martigale vs Markov Chain process?
(FERM14)
- Martingale -
- Today value is the same as the past value
- t x probability
- Markov Chain -
- Today value is independent of hte past value
- (More complicated)
What are some practical issues with credit migration models?
(FERM14)
- Credit ratings do not give a high level of granularity
- Different agencies can produce different ratings for the same firm
What are common shock models?
(FERM14)
Assumes bond defaults are linked by Poisson processes
What are Survival/Time-unti-default models?
(FERM14)
Survival function F(x) = e-ht
where the probability of default is 1 - F(x)
What are 2 reasons why liquidity is difficult to quantify?
(FERM14)
- Data on liquidity crises is limited
- Liquidity occurs in different ways (i.e., is firm-specific) so industry data is of little use for liquidity modeling
What is the most common approach used to asses liquidity risk?
(FERM14)
Stress testing
What are 7 scenarios tested for liquidity risk stress tests?
(FERM14)
- Rising interest rates
- Ratings downgrade
- Large operational loss
- Loss of control over a key distribution channel
- Impair capital markets
- Large insurance claim for a single or related events
- Sudden termination of a large reinsurance contract
What are 2 types of systemic risks?
(FERM14)
- Feedback risk
- Returns exhibit some degree of serial correlation
- e.g., a change in price will result in further changes in the same direction
- Contagion risk
- Interaction between different financial series, better modeled using copulas
- e.g., the risk that one firm fails results in further failures
What are 7 types of demographic risks?
(FERM14)
- Mortality
- Level
- Volatility - risk that mort experience will differ because there is a finite number of lives int he population considered
- Catastrophe
- Trend
- Longevity
- Level
- Volatility
- Trend
What are 2 ways to determine the current level of mortality?
How are they combined?
(FERM14)
- Experience rating
- From past mortality rates for a group of lives
- Can be used to calculate (a) central rate of mortality or (b) initial rate of mortality
- Risk rating
- From the underlying characteristics of a group of lives
Can be combined using credibility
What are two aspects in non-life insurance claims?
(FERM14)
- Incidence (frequency)
- Intensity (loss severity)
What are 2 statistical issues when analyzing claim frequencies?
(FERM14)
- Data set will often span a number of years
- Some policyholders will be included in the data set for each year, while others will not (i.e., different risk exposure)
What are 3 statistical issues when analyzing claim intensity?
(FERM14)
- Seasonaility
- Clustering
- Censoring
What are 3 approaches to determine claim reserves for high claim frequency classes?
(FERM14)
- Total Loss Ratio
- Total estimated claims = (Total loss ratio) x (Earned premium)
- Chain Ladder
- Use link ratio
- Bornhuetter Ferguson Method
- Ultimate loss = (Claims reported) + (Premium)(Loss ratio) x (Claims Outstandingchain ladder approach)
- Interim loss = (Claims reported) x (Link ratio)
What are 3 ways to assess operational risk?
(FERM14)
- Simple approach (income times a fixed percentage)
- Top-down method (residual income volatility)
- Risk capital (residual risk capital)
Why do unquantifiable risks arise?
(FERM14)
Not all risks can be quantified because the potential losses are difficult to assess (size and likelihood)
How can unquantifiable risks be assessed?
(FERM14)
Using a risk map:
What is VAR?
(VAR5)
The worst loss over a target horizon such that there is a low, prespecified probability that the actual loss will be larger
Pr(L>VAR) <= 1 - c
What are the steps in computing VAR?
(VAR5)
- Mark to market the current portfolio
- Measure the variability of the risk factor
- Set the time horizon, or the holding period
- Set the confidence level
- Report the worst potential loss by processing all the preciding information into a probability distribution of revenues, which is summarized by VAR
What are relative VAR and absolute VAR?
(Non-parametric)
(VAR5)
- Relative VAR
- Conceptually more appropriate because it views risk as a deviation from the mean
- More consistent with definitions of unexpected loss
- VAR(mean) = E(W) - W* = -W0(R*-µ)
- Absolute VAR
- VAR(zero) = W0 - W* = -W0 R***
- where
- W0 = initial investment
- R = rate of return
- µ = expected rate of return
- σ = volatility of return
- W* = quantile of the distribution
What is the expected tail loss (ETL)?
(VAR5)
ETL = Average losses beyond VAR + mean
What are relative VAR and absolute VAR?
(Parametric)
(VAR5)
What are 4 desireble properties for risk measures?
(VAR5)
- Monotonicity
- Translation invariance
- Homogeneity
- Subadditivity
What are 5 uses of VAR?
(VAR5)
- as a Benchmark Measure
- To comapre risks across different markets
- as a Potential Loss Measure
- To give an idea of the worst loss an institution can suffer
- as Equity Capital
- Used directly to set capital cushion for the institution
- as Criteria for Backtesting
- Comapre backtested VAR against P&L
- Basel Parameters
- Used to set minimum capital requirementf or regulatory purposes, equal to VAR(99, over 10 days)x3
What is maxVAR?
(VAR5)
- The worst loss at the same confidence level but during the horizon period H
- Must be greater than the usual VAR
What is the SE in the estimated mean and standard deviation?
(VAR5)
Describe the differences between parametric and non-parametric approaches on quantiles.
(VAR5)
Which method (parametric vs. non-parametric) is better?
(VAR5)
- Parametric σ-based approach is more precise, given that it provides a narrower confidence interval
- The sample standard deviation contains more information than sample quantiles
What are he formulas for EVT VAR and EVT ETL?
(VAR5)
What are the advantages and disadvantages of the parametric and non-parametric approaches to calculate VAR?
(VAR5)
- Advantages:
- easier to use
- create more precise estimates of VAR
- Disadvantages:
- may not approximate well the actual distribution of P/L
- (note: if using empirical quantiles, the effect of sampling variation or imprecision might be included in the VAR number)
When is it important to select confidence level and horizon for VAR?
(VAR5)
- Arbitrary when:
- VAR is used as a benchmark risk measure, only needs to be consistent across markets adn time
- Importatn when:
- VAR is used to decide amount of equity capital to hold
What is an alternative measure of risk to VAR?
(VAR5)
Expected tail loss (ETL), which has several advantages relative to VAR:
- ETL is stable under addition (time aggregation)
- Compensates for:
- Underestimation of potential losses of normal distribution
- Lack of data in the tails of empirical distributions
How do you calcualte portfolio VAR?
(VAR7)
where
- w = [w1 w2 … wN] = unitless weights or linear exposures to a risk factor
- Σ = N by N covariance matrix of N components
- W = initial portfolio value
note that:
σ2p W2 = w’ Σ w W2 = x’ Σ x
How is individual VAR calculated?
(VAR7)
What is the relationship between portfolio risk, correlation and number of components?
(VAR7)
How is the diversification benefit calculated?
(VAR7)
DB = Undiversified VAR - Diversified VAR
where
Undiversified VAR = sum of all individual VARs
What is marginal VAR and how is it calculated?
(VAR7)
The change in portfolio VAR resulting from taking an additional dollar of exposure to a given component.
Note that
ßi = cov(Ri,Rp) / σ2p = pip σi / σp
How is beta calculated?
(VAR7)
What is incremental VAR and how is it calculated?
(VAR7)
It is the change in VAR owing to a new position.
A drawback is that it requires a full revaluation of portfolio VAR with a new trade.
What is the best hedge?
(VAR7)
The additional amount to invest in an asset to minimize the risk fo the total portfolio.
What is the component VAR and how is it calculated?
(VAR7)
The partition of the portfolio VAR that indicates how much the portfolio VAR would change (approximately) if the given component was deleted.
Component VAR = Marginal VAR x dollar position
Sum of Component VARs = Portfolio VAR
Describe a graphical illustration of the VAR decomposition
(VAR7)
How is the percent contribution to VAR calculated for a single component?
(VAR7)
Component VAR / Portfolio VAR
What is the sharpe ratio and how is it calculated?
(VAR7)
The metric that measures how much expected excess return a portfolio can give for each unit of risk.
SRp = Ep / σp
where
Ep = expected return of the portfolio
What are 3 reasons why volatility prediction is important for risk management?
(VAR9)
- If volatility increases, VAR increases, so investors may adjust their portfolio exposure for assets which volatility will increase
- Predictable volatility means that assets depending directly on volatility (e.g., options) will change value in a predictable fashion
- In a rational market, equilibtium asset prices will be affected by changes in volatility, and those who can predict volatility can control financial markets better