try this....
http://www.bmwgroup.com/e/nav/index.html?http://www.bmwgroup.com/e/0_0_www_bmwgroup_com/investor_relations/investor_relations.html
The 2010 9 months Z4 sales worldwide were 20,637 (+21.9%). I'm not sure this is as good as it sounds though because the new model came out in May 2009. I can't remember when they stopped selling the E85/86 but you would've expected a greater percentage uplift versus a year when the model wasn't on sale for part of the time.