What is the overhead cost of an empty vector?

Question

What is the memory overhead of having an empty vector vs having a pointer to a vector?

Option A:

std::vector v;

Option B

Answer 1

VS2005:

std::vector *ptrToVec = new std::vector();
std::vector vecOfInt;

sizeof(ptrToVec) = 4
sizeof(vecOfInt) = 20

Thanks!