The country/region average values (p.7) are the estimation of the population’s average exposure based on data sampling. This is calculated from the country or region’s available city data, weighted by population. The level of air quality data granularity may vary between country and region, therefore it must be noted that this ranking is based on data sampling, and while imperfect, it is an attempt to provide a broad global overview and context between countries and regions, using the data available.

The calculation used to estimate a country’s average PM2.5 exposure based on available data and weighted by population is:

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