I'm not convinved that there is an increasing 'bias towards exclusives'. Yes, of course the exclusives are going to get preferential treatment, and they deserve to do so.
The 'disappointments' expressed by Yuri and Lisa and others, with stagnant or declining sales and income, is probably nothing other than 'dilution'.
Istock's library has increased in size by 100% over the past year. Any photographer who has NOT increased their portfolio by the same percentage will be getting reduced exposure.
Lisa, you say you've increased your portfolio by 50%, so it's axiomatic that your exposure is diluted by 25% which is very close to your reduction in sales. With 1 million new images being added each year, you are going to have to add 1,000 pictures in the coming year just to 'stand still'.
The same goes for all of us. Of course it is easier to keep a small portfolio 'ahead of the game', but with a large portfolio it is possible to reach a point where sales and income simply cannot 'grow'.
This dilution effect defines the maximum revenue available to any contributor.
I follow Hidesy's portfolio with interest simply because I have met her and her advice prompted me to start contributing to microstock a year ago; her portfolio has increased from 7,000 images to 10,000 over the last year but her monthly downloads have not improved (and appear to be in decline), so even a black diamond exclusive will hit a ceiling eventually.
This, incidentally, is also probably why Yuri's income has stopped increasing.
I agree with your points here. Exclusives can upload a lot more than non-exclusives, so there are probably lots more exclusive images on istock and it is no surprise that these come up in the search.
Does anyone know the ratio of exclusive to non-exclusive images on istock?
I wonder if some buyers will try and by from exclusives first out of loyalty to istock, or perhaps because they have more idea how many times an image has sold?
The dilution effect is probably greater with some common subjects, like business people photos, as there are so many of them and a lot of the poses are repeated many times.
The way to increase sales is to keep coming up with original and popular ideas. This gets more difficult as a portfolio gets bigger. I had lots of good ideas when my portfolio was 100 images but it is harder to think of new things with 1,000 images.