" Unclassifiable" origins: The census reports a small number
(usually well below 1% of district totals) as from "unclassifiable" places
of origin. These "unclassifiable" (together with the few "Born at Sea)" have
been reallocated to the other categories (including nonmigrants) in proportion
to each category's percentage of the total (classified) population. This is
a minor adjustment, but it ensures that users can correctly calculate, for
instance, nonmigrants from total population (record # 100) minus migrants
(record # 300).
Unknown rural/urban origin: A larger number of migrants from within
India are reported with rural/urban area of origin as unclassified. This affects
record numbers 303 (migrants from urban places) through 306 (migrants from
rural places of another Indian state). These "rural/urban origin unclassified"
are allocated to urban or rural origins in proportion to the urban or rural
origins of that category. For example, if there are 600 from rural parts of
another state, 400 from urban parts of another state, and 10 from another
state but unclassified rural or urban origins, we would adjust the data to
allocate the unclassified so that we report 606 from rural parts of another
state and 404 from urban parts of another state.
Small states: The 14 small states which the database considers as
single districts may, in fact, be divided into districts. Since the database
considers them as single districts, records 301 and 305 (migrants from another
district and migrants from a rural part of another district) have been adjusted
so that they include only migrants from outside the state.
District and state boundary changes: Users are warned that because
of geographic changes in district boundaries, the data on inter-district migrants
(records 301 and 305) are not strictly comparable over censuses. Whether migration
is interdistrict (or interstate) depends on the boundaries at the time of
the census and not on the boundaries of the 339 districts in the version 5
data set. For instance, if a district is divided into two districts between
the 1961 and 1971 censuses, we will combine data from the two 1971 districts
to recreate the 1961 boundaries; but we cannot adjust the migration data so
that in 1971 migration between the two halves will be counted as inter-district
migration in 1971 but not in 1961. The same problem applies to inter-state
migration where state boundaries have changed (e.g., Meghalaya created from
two 1961 Assam districts).
