words i need to work on

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Across
  1. 1. Description of locations on Earth's surface where populations live
  2. 5. Net migration from urban to rural areas in more developed countries
  3. 8. A mathematical formula that describes the level of interaction between two places, based on the size of their populations and their distance from each other
  4. 12. by talented, educated people
  5. 13. movement within a region
  6. 14. The ratio of the number of farmers to the total amount of land suitable for agriculture.
  7. 19. movement from one region of a country to another
  8. 20. an increase in the percentage and in the number of people living in urban settlements
Down
  1. 2. The process of population movement from within towns and cities to the rural-urban fringe
  2. 3. The number of people per unit of area of arable land, which is land suitable for agriculture
  3. 4. the level of development that can be maintained without depleting resources
  4. 6. the scientific study of population characteristics
  5. 7. hort-term, repetitive, or cyclical movements that recur on a regular basis
  6. 9. the process of change in a society's population as a combination of medical advances and economic development, affecting a population's desire and ability to control its own birth and death rates
  7. 10. the number of people under 15 and over 64 compared to the number of people in the workforce
  8. 11. The total number of people divided by the total land area
  9. 15. A measurement of the number of people per given unit of land
  10. 16. The branch of medical science that is concerned with identifying, fighting, and preventing disease.
  11. 17. medical technology from Europe and North America that was used to eliminate many diseases in the developing world
  12. 18. the portion of Earth's surface occupied by permanent human