Explaining Optimistic Old Age Disability and Longevity Expectations


Biased health care decision making has been regarded as responsible for inefficient behaviours (for example, the limited insurance purchase). This paper empirically examines two sets of biases in the perception of old age disability and longevity. Particularly, we test for the existence of a so called cumulative bias and, secondly’ a so called optimism’ bias. Findings are suggestive of a significant overestimation of disability risks but no overestimation of longevity expectations is found. Both disability and longevity perceptions appear to exhibit a ‘cumulative’ pattern when mapped over time. Healthier individuals are less likely to perceive high disability and longevity risks whilst female and younger respondents perceive a higher risk of disability in old age at a population level but not at an individual level.

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  1. 1.

    Other well known bias stems from the (under) overestimation of (un)publicised (for example, the risks from smoking) risk information (Viscusi 1990). Similarly, ‘availability effects’ (Tversky and Kahneman 1974) so that frequent events are generally easier to imagine and recall than are rare events.

  2. 2.

    However, estimates were affected by focal responses whereby some individuals reported either a 0 or 100% chance of a future event. The same applies to Gan et al. (2003), who use a Bayesian update model to account for problems associated with focal responses.

  3. 3.

    However, Walley (1991) reviews cases in which individuals consistently respond in the lower and upper ends of the probability tails when asked questions about probabilities, suggesting that numerical probabilities elicited in surveys may be consistently biased toward extremes.

  4. 4.

    The specific card provided to the interviewer included several potential causes of disability in old age offering (although not necessary assuring) a clear idea of what disability means. The aim was to inform the respondent rather than focus their attention on a specific event. Furthermore, there is evidence in the risk perception elicitation literature of the existence of ‘scope effects’ in that the explicitness of the alternatives is likely to bias the results (Windschitl 2002).

  5. 5.

    However, these estimates should be conceptualised as ‘maximum risk perception estimates’. Yet the hypothesis of morbidity compression suggests that morbidity declines as life expectancy increases (Fries 1980). Sensitivity analysis using data from Spain among other countries indicates that depending on the assumption of the effect of morbidity on old age disability, these estimates might decline by between ten and 23 per cent (Rothgang and Comas-Herrera 2003).

  6. 6.

    We employed sensitivity analysis to examine whether prior ages would matter and found that if did not.

  7. 7.

    It should be noted that this is a relatively common question phrasing employed in several studies (Purim and Robinson 2005). However, given that individuals differ in their predisposition to greater longevity, one of the main challenges of empirical studies is the correction of these measures.

  8. 8.

    This is consistent with insurance studies; the probability of experiencing losses is not directly observed, instead the probability of loss is proxied by age, gender and pre-existing beliefs (Showers and Shotick 1994).

  9. 9.

    We experimented with different age group classification by allowing people to have realistic notions of cohort differences in longevity based on their exact age, but it made no difference in the results so that we have reported then by age group instead.

  10. 10.

    Yet, this finding might well be explained by the presence of some omitted variable, capturing individual ‘optimism’, explaining both perceptions of longevity risks and health status.

  11. 11.

    Some might well argue that people who live to age 65 have a predicted life expectancy that typically takes them to an age beyond the predicted life expectancy, therefore if that were to be true, our results would imply that this feature si not taken into account.

  12. 12.

    Given that women tend to live longer, the findings suggesting no gender difference indicate once again that women might even be underestimating their life expectancy, since they may not be taking their age specific life expectancy as a reference point, but rather other forms of information from their own social network or experience.


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Correspondence to Joan Costa-Font.



See Table 4.

Table 4 Variable definitions and summary statistics (means and standard errors)

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Costa-Font, J., Costa-Font, M. Explaining Optimistic Old Age Disability and Longevity Expectations. Soc Indic Res 104, 533–544 (2011). https://doi.org/10.1007/s11205-010-9760-y

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  • Risk perceptions
  • Cumulative risks
  • Optimism
  • Longevity
  • Disability in old age