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35
votes
9answers
3k views

Lévy alpha-stable distribution and modelling of stock prices.

Since Mandelbrot, Fama and others have performed seminal work on the topic, it has been suspected that stock price fluctuations can be more appropriately modeled using Lévy alpha-stable distrbutions ...
19
votes
7answers
30k views

What is the difference between volatility and variance?

How do volatility and variance differ in finance and what do both imply about the movement of an underlying?
15
votes
4answers
809 views

Approximately what proportion of a stock’s volatility is explained by market movement?

Assume we decompose the daily (log) returns of a stock as beta times market movement plus an idiosyncratic part. If this is done ex-ante, what proportion of the variance is explained by the market ...
10
votes
5answers
10k views

Why would an investor trade a variance swap over a volatility swap?

Why would an investor trade a variance swap over a volatility swap? Is it simply related to the leverage involved in a Var (i.e. sigma-squared) or is there something else to it?
8
votes
1answer
274 views

Do weights from portfolio theory contain bias?

I want to experiment with some portfolio modelling and I was wondering if you guys could help me with something. If I try to estimate and implement the traditional two-fund portfolio consisting of one ...
8
votes
2answers
748 views

Why do low standard deviation stocks tend to have superior future returns?

I've recently stumbled on something that really surprised me. These papers (1, 2) find that past standard deviation of returns is inversely related to future returns. That is, portfolio of low ...
7
votes
1answer
3k views

Conditional or unconditional volatility?

I am reading a paper (reference below) that states "The conditional volatility for each underlying security (or for a market index) can be estimated using the standard deviation of the stock’s ...
6
votes
1answer
241 views

Variance replication using options

I would like to understand the intuition behind the following question: Why a certain weighted sum of prices of put and calls is equivalent to the implied variance of an underlying? A variance swap ...
6
votes
3answers
419 views

Variance swap replication and variance vega

Noob here. I've been trying to gain a better understanding of variance swaps and what better way than to replicate it with a portfolio of better understood instruments. I have read the GS 1999 ...
6
votes
1answer
190 views

How to scale option pricing components in regard to time

I am looking at closed-form options approximations, in particular the Bjerksund-Stensland model. I have run into a very basic question. How should I scale the input variables in regard to time? My ...
6
votes
0answers
763 views

Formula for the efficient portfolios (mean-variance optimisation)?

Consider the setting of mean-variance portfolio optimisation: $n$ assets with expected returns $\overline{r}_1,...,\overline{r}_n$ and standard deviations $\sigma_1,...\sigma_n$. For a certain fixed ...
5
votes
2answers
183 views

How to derive this approximation of the risk-neutral expectation of the variance?

On the paper Bollerslev, Tauchen and Zhou (2009 RFS) the authors say about equation (15): The corresponding model implied risk-neutral conditional expectation ...
5
votes
2answers
463 views

Choice of prior as a shrinkage target in portfolio construction?

There's various research showing how priors such as the minimum variance portfolio turn out to be a surprisingly effective shrinkage target in portfolio construction. The sell point of these priors ...
5
votes
1answer
1k views

How to calculate the conditional variance of a time series?

I am reading a paper where the term conditional variance is mentioned, but I am not really sure what is meant by this and how this can be calculated: Fig. 2 shows the conditional variances of the ...
4
votes
2answers
89 views

Does heteroskedasticity of returns depend on the time frame?

Similarly to my last question, for which I obtained very interesting and useful answers, I would like to know if there has been any study regarding heteroskedasticity and time-frames of the returns. ...
4
votes
1answer
439 views

Linear regression and assets direction prediction

I have the following asset returns Y and the predictions for the same periods Y': Y = { 10, 200, -1000, -1, -7 } Y' = { 1, 2, -3, -4, -5 } The OLR R-squared for ...
4
votes
3answers
364 views

Negative high frequency intraday volatility - Zhou estimator

To estimate high frequency tick data stock intraday volatility, I have read Robert Almgren's notes7.pdf http://www.cims.nyu.edu/~almgren/timeseries/notes7.pdf where he talks about the bias free ...
4
votes
1answer
79 views

Realized variance in SVJJ (Heston with jumps) model

I am working with the stochastic volatility model with jumps in both the price and volatility dynamics, ie. the risk neutral dynamics are of the form: $\mathrm{d}V_t = \kappa(\theta - V_t)\mathrm{d}t ...
4
votes
1answer
471 views

Calibrating Hull-White using volatility data

I would like to calibrate Hull-White model using volatility data.I am using [Park (2004)] paper as a reference. He suggests to minimize the following objective function: where the first term is ...
3
votes
2answers
960 views

Covariance for arbitrarily large portfolios

I am implementing a method in Java to calculate the variance, covariance, and value at risk for a portfolio, which should be flexible for use with any number of assets in a portfolio. I am struggling ...
3
votes
2answers
110 views

Variance of a Stock price and relationship with volatility

A bit of background. I know that the forward price of a stock (or its expected price) is given by $\mathbb{E}[S_T]=S_te^{(r-q)(T-t)}$. Here, $r$ and $q$ are not constant, but follow a curve. I was ...
3
votes
1answer
240 views

Why are there different estimators for stock volatility? (realized variance, RAV, etc)

I am very confused about why different volatility estimators (RV, RAV, BPV, etc) exist. If the goal is to find the best estimator for stock volatility, and volatility is latent, how do I know which ...
2
votes
1answer
281 views

Why is this delta-hedging/P&L example on a variance swap call correct?

I'm looking into this article about var swaps: http://sbossu.com/docs/VarSwaps.pdf and not sure how to correctly interpret Exhibit 2.1.1. "In this example an option trader sold a 1-year call ...
2
votes
1answer
244 views

How to calculate two-time scale variance?

I am having trouble understanding how to calculate two-time scale variance as I do not have a strong mathematical background. Suppose I want to calculate the TSRV at 5 min intervals. Do I calculate ...
2
votes
2answers
935 views

Should I use GARCH volatility or standard deviation in cross-sectional regression?

I want to do a cross-sectional study where the historical, medium-long run volatility of some return series (call it $R_t$) is included as a regressor. Which of the following two estimates of ...
2
votes
1answer
180 views

out-of-sample variance using rolling window

I am currently working on the comparison of the constructed portfolios using out-of-sample variance criteria. I am going to use rolling window procedure for the comparison. First, I choose a window ...
2
votes
1answer
257 views

Combining covariances?

Consider an economy with assets with return processes $A$, $B$, $C$, $D$. Consider a weighted index with return process $I=aA + bB + cC + dD$ where $a,b,c,d$ are coefficients, and $a+b+c+d = 1$. ...
2
votes
0answers
38 views

How to calculate the estimation error of portfolio variance using propagation results?

I am trying to find a conservative approximation for the propagated estimation error of a investment portfolio's variance (comprising two assets), given we know the estimation error for the variance ...
1
vote
1answer
333 views

Calculating Variance Explained from PCA Loadings

I have a return history for a universe of risky assets and I've run a principal component algorithm and obtained a loadings matrix (num_factors by num_assets) for the first 5 factors. I have a ...
1
vote
1answer
478 views

VaR Calculation - Covariance matrix is not positive semidefinite

This is a basic question. I have three assets, equally weighted, and all the mutual covariances are -1. Then, the covariance matrix looks like - ...
1
vote
2answers
107 views

Modern portfolio theory in practice

I am wondering about the Markowitz theory of portfolio construction in practice. Hence, if one wants to know the efficient frontier, what variances can one use. The only method that I can think is the ...
1
vote
1answer
50 views

What is the formula for variance in estimating exchange rate?

I was watching this Youtube Video. He used a exchange rates of Euro to Dollar for a few days and apply GARCH(1,1) to get the predicted price. However, I didnt understand variance that he calculates ...
1
vote
3answers
122 views

Is variance additive only under Log-returns?

Can't seem to figure this one out by thinking it through. Let's say that the simple return $R_t=P_{t+1}/P_t -1$ is assumed to be $R_t \sim iid N(0,\sigma^2)$. Thus, a two period return would be ...
1
vote
1answer
70 views

Variance Swap volatility

In an article, it is mentioned that a parameter is "the variance swap volatility at time t". I know what a variance swap is but I don't know what they could mean by "variance swap volatility". ...
1
vote
1answer
192 views

Basics about the scaling property of volatility

It is a usual practice to calculate realized volatility $\sigma$ using the square root of the usual variance estimator $\hat{{\sigma}²}$. This is done using the stock log returns (practitioners ...
1
vote
1answer
282 views

Minimum variance hedge with more than one asset

My portfolio comprises of 3 assets A,B,C that are correlated and the variance-covariance structure is known. At any given point in time, my position in Asset A say is given to me. I need to ...
1
vote
2answers
512 views

What is the instantaneous P&L of a Variance Swap?

What is the instantaneous P&L of a variance swap. Is it $(\sigma^{2}_{t}-\sigma^{2}_{implied})dt$?
1
vote
1answer
62 views

Static and Dynamic Hedging of Vol/Var Swaps

Why can a variance swap be perfectly statically hedged whereas a volatility swap requires dynamic hedging? Possible reference request to the corresponding literature.
1
vote
1answer
29 views

Are Variances generally stable for any given instrument?

My hesitation, as I look at getting into forecasting based on observed variances, is the nagging question - if variances are not constant per-instrument, is it any good to use the last month or year's ...
1
vote
1answer
28 views

Calculate control variate for monte carlo simulation

For an exercise I need to calculate $\mathbb{E}[X]$ with a Monte Carlo simulation. I need to use control variate $Y$ with $\text{Var}(Y)=2$ and $\text{Cov}(X,Y)=1$. I am asked to give the optimale ...
1
vote
0answers
51 views

Fourier transform covariance estimator

I am estimating realized variance and covariance by the estimator described in this paper, and relying on Fourier Transform. Now, as my data is one day of data in ultra high frequency, so that the ...
1
vote
1answer
228 views

how to compute daily skewness of S&P daily return timeseries under no other more high - frequency time series?

As we all know , return time series marked features: fat tail or negative skewness and peakedness. For a similar problem of variance computation, we can compute variance by garch model and other ...
1
vote
0answers
91 views

How to measure if variance is greater at a certain time of day?

I'm not very fluent in the quant vernacular, so perhaps the nature of my question will be better illustrated as a hypothesis. One market has closed and another market elsewhere on Spaceship Earth is ...
1
vote
0answers
540 views

portfolio optimization with a loop

I am attempting to minimize the variance of a 3 stock portfolio using optimization within a loop. What I have done is calculated the stock returns and cov matrix from dates 1980-01-01 to 1989-12-31 ...
0
votes
2answers
187 views

Geometric Variance

If the arithmetic mean is: $ \frac { \Sigma (x_i) }{n}$ and the geometric mean is $ (\prod (1+x_i) ) ^{1/n}$ The arithmetic variance is $ \frac { \Sigma(x_i-\mu)^2 } {n} $ then what is the ...
0
votes
1answer
169 views

What are the parameters of the function PORTVAR in Matlab?

According to the Matlab help, Portvar will give the "Variance for portfolio of assets" by entering the returns of the Assets and the corresponding weight. However, it does not explain the parameters ...
0
votes
3answers
94 views

Variance calculation

How could I calculate variance when I have a snapshot of a portfolio that shows the following for each stock: Purchase Price, Close Price, Change in value, Change in percentage, Shares owned, ...
0
votes
1answer
61 views

Variance covariance matrix for a portfolio containing bonds also with other asset classes

What should we take for a bond or a zero coupon bond in order to make a variance covariance matrix? For example:- Equities - we take the market price Cash - we take the spot rates Bonds - Do we take ...
0
votes
0answers
45 views

Easy question (?) - how to measure if volatility for two samples is significantly different?

For my bachelor thesis I'm doing a research where at one point I want to measure if volatility for a certain sample of stocks in period A is significantly different from i) the same sample of stocks ...
0
votes
0answers
71 views

Forecasting conditional variance using fGARCH

I am forecasting the conditional standard deviation using ARMA(1,0)-GJRGARCH(1,1) in R using the fGarch package. Here is a sample code: ...