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RIVM report 773301 001 / NRP report 410200 051 page 113 of 142
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There is no generally agreed definition of ‘rural’ and ‘urban’ population or ‘rural’ and ‘urban’ area
(Clark and Rind, 1992). Sometimes the distinction is between settlements smaller or larger than 10,000
inhabitants living in a built-up area. However, then the question is what is a built-up area: are these
households living all adjacent to each other, or are they (partly) distributed over a large area with
distances between houses of 100s or 1000s of metres? Also the definitions that countries use in reporting
their national fraction of urban and rural population to the UN Population Statistics Division differ in
practice, often to an unknown extent.
Therefore we decided to use a pragmatic approach in separating out the area and population in the
country that is living in smaller units, e.g. smaller than 10,000. Since the grid cells at 1 o x1 o can be as
large as the order of 100x100 km near the equator, many rural communities may live in one grid cell. So
taking a cut-off of 10,000 persons per grid cell would be a too simple approach. Instead we made the
following argument:
ú make the spatial distinction into rural and urban areas within a country only for the larger ones, since
for the smaller ones the spatial redistribution effects will be much smaller;
ú
ú
use a default urban population density (in pers/km 2 ) for continuously built-up urban areas based on
data for a selection of European type of cities;
if the population density of a grid cell is higher than is this urban cut-off value, we assume the cell to
be 100% urban;
ú if the population density is less than a selected rural cut-off density, we assume the cell to be 100%
rural;
ú
also if the WRWDOpopulation of a grid cell is lower is than 10,000, we assume the cell to be 100% rural;