Remember when we thought 88 billion minutes was a lot of time for Americans to spend on social networks in one month? That was so July 2011. This July, we spent 37% more time on social media than we did last year. That’s 121 billion minutes of liking, tweeting, and pinning.

While new social networks such as Pinterest have powered some of that growth, a report released by Nielsen Tuesday indicates that mobile is the biggest driver. According to the report, time spent using social media from a mobile device contributed 63% of the year-over-year growth.

Consumers increased their social app usage by 76% compared to last year, and social networking now accounts for 30% of mobile web time compared to 20% of desktop web time. It’s no wonder that Twitter, Facebook, Zynga and any social startup with a prayer of entering the social networking space have declared themselves “mobile first” this year.

Photo by Flickr user Webtreats