The effectiveness of content marketing can be measured in terms of before and after
Since it is not straightforward how to measure the success of your content marketing strategy you can evaluate your before and after bottom-line situation. So suppose your revenue was $x before the implementation of your content marketing strategy is it now $x+$n where n can be any positive number? If this seems like a very vague measure you can think in terms of getting more traffic to your website keeping other factors constant. Are you getting more traffic after implementing your content marketing strategy? This can give you an indication of how successful your campaign has been so far.