Ordering changes... ???

Hello,

Could somebody explain me why the ordering has been changed ? In these two examples. First Query returns order by empid, but why it changes in the second one ? Why everything in order by orderdate ? 

Am I missing something ? 

SELECT empid, YEAR(orderdate) AS orderyear
FROM Sales.Orders
WHERE custid = 71
GROUP BY empid, YEAR(orderdate);

This query returns the following output.
empid orderyear
----------- -----------
1 2006
1 2007
1 2008
2 2006
2 2007
2 2008
3 2007
4 2007
4 2008
5 2007
6 2007
6 2008
7 2007
7 2008
8 2007
9 2006

Second Query.

SELECT
empid,
YEAR(orderdate) AS orderyear,
SUM(freight) AS totalfreight,
COUNT(*) AS numorders
FROM Sales.Orders
WHERE custid = 71
GROUP BY empid, YEAR(orderdate);


This query generates the following output.

empid orderyear totalfreight numorders
----------- ----------- --------------------- -----------
1 2006 126.56 1
2 2006 89.16 1
9 2006 214.27 1
1 2007 711.13 2
2 2007 352.69 1
3 2007 297.65 2
4 2007 86.53 1
5 2007 277.14 3
6 2007 628.31 3
7 2007 388.98 1
8 2007 371.07 4
1 2008 357.44 3
2 2008 672.16 2
4 2008 651.83 3
6 2008 227.22 1
7 2008 1231.56 2