Parallel.ForEach Returning Values

I need to process a list of objects (not the same shown on the sample), which I thought could be greatly improved by running it in parallel.foreach loop. However, the result is not what I expected. Sometimes the returned list doesn't match with the input list. Please let me know why it is not working as I expected (novise), and also how to make it work. Please see sample code used below.

List<string> list = new List<string>() { "John", "Mary", "Margaret", "Silvia", "Martha" };

List<Person> people = new List<Person>();

Console.WriteLine("There are {0} names on the list", list.Count.ToString());

Parallel.ForEach(list, name =>
{
    people.Add(new Person(name));
});

foreach (Person person in people)
{
    Console.WriteLine("Name: {0,-10} Age: {1}", person.Name, person.Age.ToString());

}

Console.WriteLine("There are {0} people on the list", people.Count.ToString());


Console.ReadLine();

namespace ParallelForEach
{
    internal class Person
    {
        public string Name { get; set; }

        public int Age { get; set; }

        public Person(string name)
        {
            Name = name;

            Age = name.Sum(c => (int)c);

        }
    }
}