10 questions linked to/from Why and when we should use the log variable?
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### If the volatility of pounds/euros = .2 do we know anything about the volatility of euros/pounds?

I think the question here is what we know about $\mathrm{Var}\left(\frac1X\right)$. Is this the right question to ask, and if so is there anything that can be said?
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### Difference between 5Y breakeven inflation and 5Y5Y inflation forward?

I cannot figure out the difference between the two data series found here: https://fred.stlouisfed.org/series/T5YIE/ https://fred.stlouisfed.org/series/T5YIFR/ The 5Y breakeven inflation, to my ...
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### How can I measure returns such that the average is useful?

If I measure daily returns by simple percent change, a -50% day then a +50% day (or vice versa) results in a true -25% total change, but the average makes it look like you would expect a total 0% ...
1 vote
1k views

### GARCH on returns or on log-returns?

I'm trying to capture heteroskedasticity in the returns of a price time series using a GARCH model. A basic intuition suggests that I should fit the GARCH model on log-returns: indeed, if the price is ...
1k views

### Why should we use log returns? Log normality

According to this link, there are some reasons we have to use log returns. But I can not understand the first reason provided in the link: First, log-normality: if we assume that prices are ...
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### Is it possible to calculate logarithmic return for short position? [closed]

In the book "Python for Algorithmic Trading" by Yves Hilpisch, it calculates the logarithmic return by summing up all the log values. When calculates the profit for long position: log(...
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### Implied volatility and realized volatility

There are many articles and posts here claiming that the implied volatility is the expectation of future realized volatility. I don't understand. To begin with, isn't implied volatility homogeneous to ...
1 vote
319 views

### Compounding vs Annualizing Returns in a Portfolio Optimization Context

This might be a rather basic question that might be closed... but I can't for the life of me understand why in many Google search results the annualization of daily returns is done like this: r_yearly ...
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