From Linked VP Marketing Konstantin Guericke

When someone recieves a request that arrives via a referral, the acceptance rate has been quite stable in the low to mid-80's. This is very high compared to cold contacts for an average person (of course, some people are more receptive to cold contacts than others). Interestingly, it doesn't matter that much if the request came from someone two, three or four degrees away.

The rate for requests to reach the recipient varies greatly by people. If a well-known partner at a prestigious VC firm sends a request offering to invest, it is highly likely to get forwarded (BTW, this is LinkedIn got funded). Contrast this with someone who has one or more of the following "risk" factors for their request:

1) Little info on profile

2) Few connections or excessive number of connections

3) No endorsements

4) Little work experience

5) Lack of impressive titles/companies in background

6) Vague request text--not clear what is asked

7) Typos on request text

8) Request looks generic--not tailored to recipient

9) Request text without convincing value to targeted recipient

10) Request text does not match chosen request type or any of the request types to which recipient is open

11) First forwarder adds no value ("just forwarding this on" or "can you please help my friend") instead of putting some skin in the game and explaining why they are making the introduction

12) Request target if four degrees away

13) Recipient is very sought-after person and closely guarded by their connections

Any of these factors will lower the chances that the request will make it to the recipient. This exmplains why reach rates vary a great deal from person-to-person, while accpetance rates have stayed quite stable.