From ShareThis …

Sharing vs. Search:
Many of our publishers are seeing increasing results from sharing. Here are a few network-wide observations. Stay tuned to our blog and site for more insights in coming weeks.

* Sharing can make up 5-10% of your overall traffic.
* Sharing can make up 15-30% of your search traffic.
* Sharing drives 25-50% more engagement (page views/unique) than search.