无法推导模板参数

我试图使用 std :: transform 将两个相等大小的向量合并成一对向量。

I'm trying to use std::transform to merge two equal size vectors into a vector of pairs.

int main()
{
    vector<string> names;
    // fill it with names    
    vector<int> nums;
    // fill it with numbers

    typedef pair<int,string> Pair_t;
    vector<Pair_t> pv;

    transform(nums.begin(), nums.end(),
              names.begin(), back_inserter(pv),
              make_pair<int,string>);
}

VC10给我：

'_OutIt std::transform(_InIt1,_InIt1,_InIt2,_OutIt,_Fn2)' : could not deduce template argument for '_OutIt' from 'std::back_insert_iterator<_Container>'
          with
          [
              _Container=std::vector<Pair_t>
          ]

那么为什么不能推导出模板参数呢？

So why can't the template argument be deduced? And how do I fix it?