Here is a quote from http://submit.shutterstock.com/forum/viewtopic.php?t=130239&postdays=0&postorder=asc&start=135
At Shutterstock, we perform regular tests of small modifications to search. Those tests are typically released to limited segments of the overall customer population. If a test wins over time – which typically means that the changes have demonstrably increased the total number of customer downloads – then the resulting improvements are accepted and deployed.
Search testing and analysis is a continuous process of small improvements that generally won’t result in dramatic swings in search. Changes are carefully tested and evaluated to make sure that the overall effect on customer downloads and/or purchases is a positive one.
Customer demand, content differentiation, keyword quantity and quality, global holidays, seasonality and other factors can affect an individual contributor's day-to-day earnings. We recommend allowing a little time before evaluating the effect on your personal portfolio.
Sincerely, Anthony Correia Director, Contributor Success Shutterstock|Bigstock
So yes, many of us have been experiencing a swing of downloads from time to time. Shutterstock is doing testing on what can contribute to the best result. I wouldn't say this is a bad thing because afterall, the most important thing is, customers need to be able to find the images they want in the shortest possible time. That would then be able to retain a customer for a longer period of time.
So, what should we do now? There are two things that we can do in order to minimize our risks from this.
- Title and keywords. Shutterstock may change the weight given to the number of keywords we put in, and the length of title as well. So, as a contributor, mix your uploads with different quantity of keywords (in the title as well).
- Time of upload. You should upload frequently, and not upload hundreds of file in one shot. This is because the freshness of your files may also contribute to the factor.
I totally support Shutterstock hard work on this because this is an important factor that contribute to our success.