def sum_of_lists(lists):
    """Aggregates list of numeric lists by summing."""
    if len(lists) == 1:
        return lists[0]

    # Preserve datatype
    size = len(lists[0])
    init_val = type(lists[0][0])(0.0)
    total = [init_val] * size
    for ll in lists:
        for i in range(size):
            total[i] += ll[i]
    return total