Which metric measures the percentage of people who take a desired action after being exposed to a campaign?

Conversion rate measures the percentage of users who complete a desired action, such as making a purchase, filling out a form, or clicking a link, after interacting with a campaign. It directly reflects campaign effectiveness in achieving specific goals. ROI (Return on Investment) measures the financial gain relative to the cost of an investment, not specifically the percentage of actions taken. Reach refers to the total number of unique individuals who saw the campaign, not those who acted. Bounce rate measures the percentage of visitors who leave a website after viewing only one page, which is a website-specific metric and not directly tied to campaign action completion.