Positive effects.
•    Availability of labour force for agricultural and industrial production
•    Increased market for the available goods and services
•    Optimum utilisation of the available  opportunities/ resources
•    Opening up of formally unutilised land and other natural resources like swampy areas.
•    Development of infrastructure for example roads, schools, hospitals etc
•    Development of urban centres etc.

Negative effects of receiving areas.
•    Over crowding / congestion leading to diseases
•    Poor housing facilities –development of slums  
•    Pollution of environment/poor waste disposal.
•    Unemployment-more people than existing jobs.
•    High crime rates / prostitution / thuggery
•    Shortage of food /high prices
•    Strain on social services/ amenities
•    Land disputes/ lack of space for expansion
•    Strain on natural resources
•    Moral degeneration.