add_gdp_column          Add GDP to Country Data
add_gov_exp_column      Add Government Expenditure to Country Data
add_gov_exp_share_column
                        Add Government Expenditure as Share of GDP to
                        Country Data
add_income_level_column
                        Add Income Levels to Country Data
add_iso3_codes_column   Add ISO-3 Codes to Country Data
add_population_column   Add Population Column to Country Data
add_population_density_column
                        Add Population Density Column to Country Data
add_population_share_column
                        Add Population Share Column to Country Data
add_poverty_ratio_column
                        Add Poverty Ratio Column to Country Data
add_short_names_column
                        Add Short Names to Country Data
