The website M-rank.net is a very useful tool for all contributors who sell vector graphics on Shutterstock. The website tracks the top 100k vectors on the agency’s database and compares the collected statistics. All data is free and public, but the contributor needs to have at least one file in the top to appear on M-rank.
After being listed, you can access stats about your

• rank (= the sum of ranks of all the top vectors in the portfolio),
• total amount of vectors (and the dynamics of your uploads),
  
• marketability (= the coefficient of the average popularity of the vectors in your portfolio)
• best vectors (icon list with rank development of single top graphics)

In addition your can check great statistics about the Shutterstock database in general here.

Shutterstock Statistics about the growth of the database – Source: m-rank.net (6/4/2016)

Statistics about the poortfolio structure of the top 100k vector contributors on Shutterstock – Source: m-rank.net (6/4/2016)

Another nice feature of the website is the compare with neighbors function; here you can directly compare your stats to those contributors with a similar ranking. This allows beginners as well as experienced designers to see how effectively they are really working and what kind of vectors are selling well in other portfolios.
I hope that in the future, there will be this kind of detailed statistics not only for Shutterstock, but also for other stock agencies!