It will probably be difficult to find these numbers specifically. Especially since Twitter and Facebook aren't really designed for converting clicks to sales. These social networking platforms are primarily for engaging and connecting with one's target audience with the side benefit of possibly increasing sales. If someone is only looking to use social media for the sake of sales, then they may be disappointed since that's not where the true value of social media lies. It would be important to create an entire social media marketing strategy for engaging, connecting and increase overall visibility...this, in turn, may lead to more sales.
There are ways to track whether a referral from Twitter or Facebook ultimately results in a sales using one's web analytics but that is beyond my knowledge base. You'd have to a search on that specifically.
I highly recommend reading this post and/or referring your client to read it as well to gain a better understanding.
ROI vs. “Impact on X” – Understanding what Social Media ROI is and isn’t.
Mashable also had a
post recently that indicated there was about a 2.8% click through rate on links posted on Twitter. There was some debate about the methodology though. However, what this does tell you is that the rate at which people click through on a link can be rather low, so a sales conversion rate is probably even lower if one is only posting links. This where it would be important to create an entire strategy for using social media.
Twitter and Facebook conversion rates
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