The scales below illustrate the full range of female and male values for each of the 14 indicators of the Global Gender Gap Index. Female values are represented by grey circles below each horizontal axis; male values are represented by blue circles above each axis. Dark blue circles are used for the Wage equality for similar work and Sex ratio at birth indicators. Minimum and maximum possible values are positioned on either end of each scale. For Wage equality for similar work, this is a scale of 1 (worst value for women) to 7 (best value for women). For Estimated earned income the maximum value is 40,000 US dollars; this is the benchmark used in the calculation of the Index. For Sex ratio at birth (female / male) the maximum value is a ratio of 0.944; this is the benchmark used in the calculation of the Index. For Healthy life expectancy, the maximum value listed is that of the countries with the best performance on this indicator (78 years). For Years as head of state the minimum value is 0 years and the maximum value is 50 years. All other indicators are expressed as percentages with a minimum value of 0% and a maximum value of 100%.