user: Question: What is the population in millions for 2011 where the GDP (nominal) (billions USD) is 4? 
Columns: ['Country', 'Area (km²)', 'Population (millions, 2011)', 'GDP (PPP) (USD, per capita)', 'GDP (nominal) (billions USD)', 'HDI (2011)']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Algeria', '2,381,741', '37.1', 7200.0, '183.4', '0.698 (medium)']
SQL:

assistant: SELECT "Population (millions, 2011)" FROM "Table" WHERE "GDP (nominal) (billions USD)" = '4';