A lot of link builders have been struggling with the correct ratio of anchor text after the Penguin update. Below is a suggestion by mMatt Cullen who Many SEO’s have a lot of respect for:

“Pre-Panda/Penguin, there was a pretty specific formula that would
work the majority of the time for ranking a website in Google.
Obviously, this was dependent on the competition too, but the key
strategies went something like this…

1. Get a bunch links – a lot of them

2. Get links with your keyword in them

The formula looked like this:

– 60% of your links should be your main keyword

– 15% of links are your main keyword + other words (eg: read about,
check out, etc)

– 15% of your links generic text (eg: click here, visit site)

– 10% of your links as the text (eg: your link URL used as the text)

And like a lot of people have experienced, when Google’s
Penguin update came around, it effected this “formula”.

BUT there’s one very good reason that some of our sites
didn’t get hit at all, or recovered extremely fast. And it has
absolutely NOTHING to do with where we were getting the links from,
but more so with “how” we were linking… i.e. the link
density and anchor text we were using.

We quickly realized that the old way of doing things needed to be
changed. Slamming your sites with a bunch of keyword rich anchor
text is finished – it won’t work.

But the reason we’ve now rebounded is because of the following
two things:

1. It wasn’t the links that were the problem

Getting a ton of links still works. Do I need to repeat that?

Most people froze and just stopped building links altogether
fearing that if they continued, their sites would get hit even
harder.

They were wrong. You see I figured that if you suddenly stopped
business as usual, that it would be a sure-fire sign to Google that
you were up to something and then they would hit you even harder.

They were looking for a reaction on your part. If something
suddenly changes, you’re likely gaming the system. If your
links are in fact natural, well then why would anything change?

It wouldn’t…

So we got that part right and now we’re almost back to
pre-Penguin traffic levels and rankings.

But there was a second thing…

2. Anchor text links have CHANGED…

Our formula for the amount of keyword anchor text we used was now
defunct. We didn’t change it right away (keeping with what I
outlined above), but we did slowly phase in a new formula.

The new formula goes a little something like this (obviously
adjusting as needed, based on our competition too):

20% – your main keyword that you’re wanting to rank for

25% – related LSI keywords (these are keywords related to your main
keyword. Think of these as the “related” searches that
Google shows you as you’re typing in their search field).

35% – your URL as the anchor text, as well as other combinations of
“branded keywords”.

20% – generic keywords

Google is now looking for a more diverse linking profile – a more
natural one.”