This past March Google indicated that they would be doing another mobile-friendly update. This is following the major update they did in April of 2015 - dubbed "Mobilegeddon", which increased the importance of having a mobile-friendly website for rank within mobile device results. Though it may not have been the doom and gloom that was anticipated, Mobilegeddon did have a significant impact on websites that are not yet responsive or have a unique mobile website.
Last month, on May 12th, Google confirmed that this newest mobile-friendly update had completed its rollout, which was done over several weeks. This update was specifically designed to increase website mobile-friendliness as a rank factor. According to Google this was, "an update to mobile search results that increases the effect of the ranking signal to help our users find even more pages that are relevant and mobile-friendly." Google uses over 200 factors to rank a website in their results, but mobile-friendliness seems to be an increasingly important one.
Is your site mobile-friendly? If you're not sure, Google has a mobile-friendly website test.