Why may net domestic product sometimes be a better indicator of sustainable welfare than GDP?

Correct answer: Because it deducts consumption of fixed capital

The gross-net distinction is central: net domestic product equals GDP minus consumption of fixed capital, commonly called depreciation. Depreciation represents the value of machinery, buildings and other fixed capital used up during production. By deducting this amount, NDP indicates the output remaining after maintaining the capital stock, so it can be more informative for sustainability than GDP. It does not, however, capture every environmental cost.