Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the population in millions for 2011 where the GDP (nominal) (billions USD) is 4?

### Inputs:
table_name: table, columns: ['Country', 'Area (km²)', 'Population (millions, 2011)', 'GDP (PPP) (USD, per capita)', 'GDP (nominal) (billions USD)', 'HDI (2011)']

### Response:
SELECT Population (millions, 2011) FROM table WHERE GDP (nominal) (billions USD) = 4