CREATE TABLE table_name_90 (gdp_per_capita__us$_ VARCHAR2, gdp__billion_us$_ VARCHAR2)

What is the per-capita GDP for the country with an overall GDP of 156.640?
SELECT gdp_per_capita__us$_ FROM table_name_90 WHERE gdp__billion_us$_ = "156.640"
SELECT "gdp_per_capita__us$_" FROM "table_name_90" WHERE "156.640" = "gdp__billion_us$_"