Because of new tech in farming, less people needed to work as a farmer so the shift began from the farm to the city. People moved to the city to get jobs in the new factories running on steam power created by burning coal. Amazing new technology was created in the city. The steam engine, generated electricity by burning coal and creating steam, new medicine and vaccines, better nutrition, underground sewers systems, flush toilets. All these advances in technology meant people were living longer and the infant mortality began to decrease, so the population of the planet grew very quickly. Fast growth rate.
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