Work Out Your EPC
A great metric for analysing your site’s earning capacity is Earnings Per Click (EPC). Calculating your EPC is simple:
EPC = Earnings / Clicks
For example, if you had a site earning $4/day on 10 clicks, your EPC would be $0.40.
While EPC fluctuates depending on what advertisers are willing to pay for a top spot, it is clear that the industry your site is in can have a major impact on EPC.
Analysing EPC can be a great way to determine which of your sites you should put energy into developing.
So what industries pay the big bucks? Well, that part you’re going to have to work out yourself. It shouldn’t be too hard. 
One thing to keep in mind however is there are no hard and fast rules about what industry is best. Sometimes you’ll earn a lot more $$ focusing on a niche market.
The other problem is if you make a site of a certain genre purely because the industry has a high EPC you’re mad. You need to write about something you’re passionate about otherwise you’ll lose motivation. And please don’t go down the dreaded path of paying others to write mundane content for you - the net is full of enough rubbish already thank you! 