Theory:

A wide range of factors is responsible for the migration of the population. Based on the effect which is causing such migration, it can be categorised as favourable and unfavourable factors. The favourable factors (positive factors, i.e. work or economic opportunities, to join family, or to study) that attract people towards a location are called pull factors.

The unfavourable factors (negative factors, i.e. to escape conflict, persecution, terrorism, or human rights violations) which make the people move out from a location are called push factors. The movement in response to the adverse effects of climate change, natural disasters, or other environmental factors are also categorised as push factors. The various causes which are responsible for human migration are categorised under five groups as follows.
 
 
Pull factorPush factor
Natural Causes
Least Hazard prone zonesHazard prone zones
Favourable climateClimate change (including extreme weather events)
Abundance of natural resources and minerals (e.g. water, oil, uranium)Crop failure and scarcity of food
Economic cause
Potential for employmentUnemployment
Socio-cultural cause
UnificationFamily conflicts
Demographic Cause
UnderpopulationOver population
Political Causes
Political securityWar, civil, unrest
Independence and FreedomSafety and security concerns (ethnic, religious, racial or cultural persecution
Affordable and accessible urban services (including healthcare, education, utilities and transport)Inadequate or limited urban services and infrastructure (including healthcare, education, utilities, transport and water)