Saturday, April 15, 2017

Today’s news “World’s oldest person dies at 117 years” - From a statistical perspective

Holiday Special Update

I am on a summer vacation this week. There will not be regular daily updates but a holiday special update. I will look at the News published today in BBC on 16 April 2017, “World’s oldest person dies at 117 years” from statistical perspective. This lady hails from Italy and the average longevity of an Italian female is 84.8 years (source: http://www.worldlifeexpectancy.com/italy-life-expectancy). Italy ranks top sixth in 2015 in the global ranking of average life expectancy. Average life expectancy is a development indicator of that country. Higher average life expectancy means higher standard of living and better health care facilities provided by the government. Many questions arise in our mind as we read this news. Some of them are the following.
1.       What is it like to be the world’s oldest person?
2.       What is the probability of being world’s oldest person?
3.       What is the probability of being in a country’s top 2% longest living people?
Life Tables tries to address these questions and gives the mortality experience of a group called Cohort. l(x), q(x), L(x), T(x) and e(x) are some of the columns of Life tables. l(x) gives the conditional probability of surviving till age x given that a person has lived till age x-1. q(x) is the conditional probability of dying before age x given that the person has lived till age x-1. L(x) is the number of person years lived between x-1 to x. T(x) is the total number of person years lived till age x. e(x) is the average life expectancy at age x. The values of this life table are governed by the current mortality experience.
I will focus on the last column of life tables that is e(x) and specially on average life expectancy at birth e(0).  The average life expectancy of a Nepalese Woman is 67.97 years (Source: Population Monograph of Nepal 2014). Due to vast rural and urban differential in health facilities which are common to all developing countries, it is 71 years in urban area and 68 years in rural areas. This implies that under given health conditions and under given socioeconomic conditions a woman on average lives till 71 years in urban areas of Nepal. If this woman belongs to rural areas, she is exposed to the socioeconomic status and health conditions of rural areas and lives till 68 years on average. This is a very promising figure indicating that a woman of Nepal has 67.97 years to fulfill all her dreams and aspirations. In contrast to Nepal a woman from Italy has 84.8 years to meet all her dreams and aspirations. So she has on average 17 more years to live. The Italian lady mentioned in the BBC news today exceeded every Italian citizen with an average life expectancy of 82.7 years (Source:http://www.worldlifeexpectancy.com/italy-life-expectancy) by living till 117 years.  
The life expectancy at birth for a female in Nepal has increased from 28.5 years in 1954 to 67.9 years in 2011 (Source: Population Monograph of Nepal 2014). This is due to increasing modern health facilities that have reduced death rates such as maternal mortality rates, infant mortality rates and child death rates. If we assume that the standard deviation is 2 years then what is the age for top 2% in terms of female life expectancy for Nepal. The average life expectancy is normally distributed. The women living higher than 72 years comprise the top 2% of the female population given that the average longevity is normally distributed with mean 67.9 years and standard deviation of 2 years.  This is under the current mortality conditions. This portrayed in the image below.



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