Appears to be no more than 10-15% per month, is that correct? Also, along the same lines, what the max amount of outbound link a site can start out with and not be canned as spam.
It really depends on the industry some industries are very web savvy and get lots of links easily where others are not. Majestic SEO has a really neat tool that allows you to compare backlinks over time of different domains.
The types of links also impact how Google views them if you are doing something that generates a lot of news and Google sees a lot of trusted news sources covering the topic and a spike in searches for the topic they would expect to see a lot of new backlinks quickly whereas if you are submitting to 1,000 directories a day and getting no other links that would throw up red flags.
Natural grow rates for incoming links? What do you think they are, plants?
There is no such thing as "natural" when dealing with incoming links, if you create quality content that is considered linkable then it will be linked. If not, it wont.
The "natural rate" of your outgoing links from your site is just as fast as you can type ... there is no such thing as X outgoing links per month.
I don't mind getting flagged, but this question is just so stupid it amazes me.
How can you even count links using percents?
Or is this deliberate flame bait?
Ok, now the proper answer:
To see a large amount of outgoing links, see wikipedia as example. If you would build a time machine and transfer wikipedia into a time it didn't exist, and it would just appear out of nowhere - then the links on it will NOT be considered spam. Because the content is of high quality.