Fresh off the announcement of their paywall experiment, Politico says it plans to expand its current subscription-based service, Politico Pro, to include trade, agriculture, and education. The company plans to launch even more Pro verticals in 2014. Dylan Byers has the memo, which offers some details into how Politico thinks about making its money:

We believe any successful media company in this age must have multiple revenue streams. In our early years, we were 100 percent reliant on issue advocacy advertising, mainly in print. That worked very well for us, and still does. But a growing newsroom must be supported by a growing business, so we have introduced events and subscriptions over the past 36 months. We still get the vast majority of our revenue from advertising, with online ads growing the fastest. But we project subscriptions will account for 25 percent of our revenue this year and close to 50 percent by 2016, providing the company a nice, sustainable balance. The beauty of subscription revenue is that it’s predictable and not dependent on broader economic and market trends. Like clockwork, more than 95 percent of Pro subscribers renew each year and the few that drop are usually members of Congress who lost reelection or companies that went out of business or merged. In almost every case, Pro subscribers often add new verticals — or more users — to their package each year.