Summary of the impact of the change from IMD2015 to IMD2019 on the slope index of inequality in life expectancy at birth
February 2020
Introduction
In September 2019, an updated deprivation index was published by the Ministry of Housing, Communities and Local Development: the Index of Multiple Deprivation 2019 (IMD2019). IMD2019 has been produced using the same approach, structure and methodology as the Index of Multiple Deprivation 2015 (IMD2015), but incorporates some small changes to the underlying indicators, and uses more up to date data.
Public Health England’s approach for production of the Public Health Outcomes Framework (PHOF) overarching indicators of inequality in life expectancy is to define deprivation deciles using the version of IMD which most closely aligns with the time period of the data. Therefore, IMD2019 has been used to define deprivation deciles for the production of the slope index of inequality (SII) indicators for 2016-18.
In order to assess the impact of using IMD2019 rather than IMD2015 for the latest data, figures for the SII in life expectancy at birth for 2016-18 were calculated using both IMD2019 and IMD2015 to define deprvation deciles and an analysis of the differences undertaken. This document summarises the findings.
An accompanying document shows charts of the data for each area.
Impact of the change at England and region level
There was no significant difference in the SII values calculated with IMD2019 and those calculated with IMD2015 for England, or for any of the English regions.
Differences between the SII values using the different versions of IMD were small. For England as a whole, there was a difference of 0.1 years for both males and females. At regional level, the differences ranged from 0 in several regions, to 0.4 years for males in London.
Table 1: Summary table of differences in SII value for 2016-18 for England and regions between calculations based on deprivation deciles defined using IMD2019 and deciles defined using IMD2015
Impact of the change at local authority level
There was no significant difference in the SII values calculated with IMD2019 and those calculated with IMD2015 in any local authority, and in the majority of local authorities the difference between the two figures was small.
In 71% of local authorities for males and 59% for females the difference in the SII value was less than 0.5 years, and the difference was less than 1 year in 93% of areas for males and 84% of areas for females.
There were a small number of local authorities with larger differences in SII values calculated with the different versions of IMD. For males, there was one local authority where the difference was greater than or equal to 2 years, and for females, 10 local authorities where this was the case. Local authorities where the difference was greater than or equal to 2 years are listed in table 3 below.
Figure 1: Histogram and boxplot showing the difference in SII value for 2016-18 for local authorities between calculations based on deprivation deciles defined using IMD2019 and deciles defined using IMD2015
