Yep, sorry about not good link. Here is better one: http://www.tippingresearch.com/uploads/managing_tips.pdf http://www.tippingresearch.com/uploads/managing_tip

Yep, sorry about not good link. Here is better one: http://www.tippingresearch.com/uploads/managing_tips.pdf http://www.tippingresearch.com/uploads/managing_tips.pdf Yes, there is a correlation, but it is extremely weak.