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Stephen Richards

Managing Director

Articles written by Stephen Richards

A likely story

The foundation for most modern statistical inference is the log-likelihood function.  By maximising the value of this function, we find the maximum-likelihood estimate (MLE) for a given parameter, i.e. the most likely value given the model and data.  For models with more than one parameter, we find the set of values which jointly maximise the log-likelihood.

Tags: Filter information matrix by tag: Makeham, Filter information matrix by tag: log-likelihood

Do we need standard tables any more?

Actuaries are long used to using standard tables. In the UK these are created by the Continuous Mortality Investigation Bureau (CMIB), and the use of certain tables is often prescribed in legislation. As actuaries increasingly move to using statistical models for mortality, it is perhaps natural that they should first consider incorporating standard tables into these models. But are standard tables necessary, or even useful, in such a context?

Tags: Filter information matrix by tag: standard table, Filter information matrix by tag: GLM, Filter information matrix by tag: survival models

New SAPS tables

On 31st October 2008 the CMIB published the new SAPS S1 mortality tables based on the mortality of defined-benefit pension schemes. These tables follow the previous release of the '00 Series' mortality tables based on the mortality of life-office pensioners. 
Tags: Filter information matrix by tag: standard table

Why we don't fit models in Excel

Actuaries are very heavy users of spreadsheets, especially Microsoft® Excel.  One question we are occasionally asked is why we wrote our software in C++, instead of letting people have direct access to our code as a spreadsheet. 
Tags: Filter information matrix by tag: spreadsheet, Filter information matrix by tag: Excel, Filter information matrix by tag: C++

Competing risks

Survival models are models for continuous risk, e.g. the force of mortality, μx.  We showed in an earlier post why this is more powerful and efficient than modelling the rate of mortality, qx
Tags: Filter information matrix by tag: force of mortality

Mortgages and annuities

Another week, another giant financial institution comes crashing down.  This time it is the turn of HBOS, a large UK mortgage provider.  The problem was not one of leverage as such, since all banks are highly leveraged.
Tags: Filter information matrix by tag: leverage, Filter information matrix by tag: mortgages, Filter information matrix by tag: annuities

Degrees of freedom

In an earlier post questioning whether we still need standard tables, we used the AIC to choose between models.
Tags: Filter information matrix by tag: degrees of freedom, Filter information matrix by tag: AIC, Filter information matrix by tag: standard table

Leverage in the annuity business

The recent bankruptcy filing for Lehman Brothers follows hard on the heels of the forced takeover of Bear Stearns earlier this year. Debt played a role in the demise of both: as with many banks and other businesses, they used borrowed money to enhance shareholder returns, a phenomenon known as leverage.
Tags: Filter information matrix by tag: leverage, Filter information matrix by tag: annuities

Features of the survival curve

 The survival curve is simply the proportion of lives surviving to each age
Tags: Filter information matrix by tag: Lee-Carter, Filter information matrix by tag: P-splines, Filter information matrix by tag: ARIMA

US Presidential survival

Senators Barack Obama and John McCain are now the confirmed candidates for their respective parties in the forthcoming US presidential election.  Much comment on Senator McCain surrounds his age (72 as at 29th August 2008), against that of Senator Obama (47, as at 4th August 2008).
Tags: Filter information matrix by tag: Barack Obama, Filter information matrix by tag: John McCain