This past week, one of my teams was working on a client issue. There was a flurry of emails sent back and forth, each one a draft of the message that might be sent to the client in an attempt to resolve the issue. Different people had different ideas about the right strategy and the right words, each of them different enough to cause many conversations.At some point, I remembered something that I know to be true: effectiveness is more important than efficiency. While there is nothing wrong with crafting a message, there is something wrong with choosing the wrong medium for the conversation. I had met the CEO a few times, and I decided to call him. It was 11:00 PM where he was, and he took my call. In just under twenty minutes, not only was the issue resolved, I would argue that our relationship was much improved.There is a difference between being efficient and being effective. Efficiency is doing things faster, with greater ease, and with less effort. Effectiveness is about producing an outcome.It is efficient to send an email, the effectiveness of which can only be measured by the outcome, the action or response of the party that receives it. If you seek effectiveness, then a different medium for that message might make for a better choice (I’d argue that face-to-face is the right choice for the most important conversations, especially ones in which you are asking for something).The Pareto principle, which seems to be some law of nature, shows that around 80 percent of your results come from around 20 percent of your actions. About 80 percent of your revenue likely comes from approximately 20 percent of your clients, plus or minus.This being true, it would make sense that effectiveness be the goal in the 20 percent of activities responsible for creating 80 percent of your results. Efficiency might be a better goal for the 80 percent of things that don’t move the needle.