Modelling excess mortality of the unemployed: choice of scale and extra-Poisson variability

"Occupational mortality and morbidity is usually studied via standardized mortality (or morbidity) ratios, with little attention to the basic fit of the implicit underlying proportional hazards model. This paper presents a case study on unemployment and mortality, based on the complete Danish male population aged 20-64 years at the 1970 census. The effect of unemployment on the age-specific mortality rate is intermediate between additive and multiplicative and was fitted well by an additive effect on the square root of the mortality. The paper discusses and illustrates whether finer stratification or random residual variation ('frailty') is to be preferred for obtaining a statistically satisfactory fit."