Your boss asks you to report on how your content campaign has contributed to his lead generation goals. What metric do you report on to demonstrate its contribution?

Total leads generated from your campaign

Explanation:

If the boss want to know how the content campaign has contributed to lead generation goals, this means that the main aim of this campaign is lead generation for now. In this light, the metrics to be reported on to show how the content campaign is contributing is simply to report the total leads that you have been able to generate from the campaign. It is about leads generation, and not about closing sales or converting leads, hence this metrics will be satisfactory.