Why, the masses of people that Google send him simply because he puts quality content on his site....
:picks himself up after laughing off his chair:
Okay, humour/sarcasm aside ... what +Dan Petrovic
says is correct ... you need to point at least a few people to the content.
The content has to "work" for them ... and they have to be the right "type" to share ... and there should be some "benefit" for the share.
As I doubt a reward scheme would suffice, it therefore has to be "attention" and "discoverer" value ... so the content itself has to be worth it, and worth it enough to pass on a little glory.
That's no small feat.
You're not exactly a "huge" name that allows you to output dross/crud and get it shared because of your "personal brand" (which I think is a good thing :D).
You're in for a hard bout ... but I'm sure you'll come up with something (you are after all not only smart, but interesting - and to be honest ... I've come close to monitoring your site a few times in the past ... and I'm damned fussy!).
Another avenue you could look at is wooing some disseminators. Find some G+ers that circle you that share more often, put them in a special circule and cultivate relationships. You could also look at people who run/participate in curation sites and do the same.
Basically seek out a new audience here ... one that consists of those that "do share".