The rate that new tokens are generated was set to 9.5% per year starting in December 2016, and decreases at a rate of 0.01% every 250,000 blocks, or about 0.5% per year. The inflation will continue decreasing at this rate until it reaches 0.95%, after a period of approximately 20.5 years (75% to content creators, 15% to Steem Power holders, 10% to Steem witnesses).