Stephen Richards Profile Picture

Stephen Richards

Managing Director

Articles written by Stephen Richards

Seasonal mortality and age

In two previous blogs (here and here) I looked at excess winter mortality.  A first glance at the charts shows that the elderly dominate the death counts.  However, the elderly also happen to provide the bulk of deaths at any time of year, so how can we be sure that they are more vulnerable to seasonal variation?
Tags: Filter information matrix by tag: season, Filter information matrix by tag: winter

The Hermite model of mortality

In Richards (2012) I compared seventeen different parametric models for modelling the mortality of a portfolio of UK annuitants. The best-fitting model, i.e. the one with the lowest AIC, was the Makeham-Beard model:

\[\mu_x = \frac{e^\epsilon+e^{\alpha+\beta x}}{1+e^{\alpha+\rho+\beta x}}\qquad(1)\]

Tags: Filter information matrix by tag: Hermite splines, Filter information matrix by tag: extrapolation

Mortality down under

Different countries have different mortality characteristics, and this is true even where countries have similar levels of wealth and development.  However, different countries also have shared mortality characteristics, and one of these is seasonal variation. 
Tags: Filter information matrix by tag: season, Filter information matrix by tag: winter, Filter information matrix by tag: cause of death

Is your mortality model frail enough?

Mortality at post-retirement ages has three apparent stages:

  1. A broadly Gompertzian pattern up to age 90 (say), i.e. the mortality hazard is essentially linear on a logarithmic scale.

  2. The rate of increase in mortality slows down, the so-called "late-life mortality deceleration".

Tags: Filter information matrix by tag: late-life mortality deceleration, Filter information matrix by tag: frailty, Filter information matrix by tag: heterogeneity

Hedging or betting?

Last week I presented at Longevity 14 in Amsterdam. A recurring topic at this conference series is index-based approaches to managing longevity risk. Indeed, this topic crops up so reliably, one could call it a hardy perennial.

Tags: Filter information matrix by tag: basis risk, Filter information matrix by tag: concentration risk, Filter information matrix by tag: model risk

'D' is for deficiency

The United Kingdom has long had persistent regional disparities in mortality, and thus in life expectancy.
Tags: Filter information matrix by tag: Scotland, Filter information matrix by tag: sunshine, Filter information matrix by tag: Vitamin D

Valuing liabilities with survival models

Regular readers of this blog will know that we are strong advocates of the benefits of modelling mortality in continuous time via survival models. What is less widely appreciated is that a great many financial liabilities can be valued with just two curves, each entirely determined by the force of mortality, \(\mu_{x+t}\), and a discount function, \(v^t\).

Tags: Filter information matrix by tag: survival curve, Filter information matrix by tag: curve of deaths

Testing the tests

Examining residuals is a key aspect of testing a model's fit. In two previous blogs I first introduced two competing definitions of a residual for a grouped count, while later I showed how deviance residuals were superior to the older-style Pearson residuals. If a model is correct, then the deviance residuals by age should look like random N(0,1) variables.

Tags: Filter information matrix by tag: deviance residuals, Filter information matrix by tag: autocorrelation, Filter information matrix by tag: Fisher transform