What factors contributed to the worlds overall population growth in the last 150 years

Fertility rates declining
international migration
mobile population
natural increase

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey

Iwould say silver and gold