This may not be the type of response you were looking for, but I think this type of answer will be more constructive for you in terms of an effective strategy.

What you should be re-examining is NOT which agencies will produce the greatest return for you.  Looking over your portfolios, and stats such as your downloads per image at Dreamstime, should tell you that the content you're creating is not connecting with buyers.  There's nothing technically wrong with it.  You're a good photographer.  Don't take this as a slam against your skills.  Far from it.

I think the problem experienced by many who frequent this forum is that there's a disconnect between what YOU WANT to upload and what BUYERS WANT. 

Eliminating the smaller agencies from your mix so you can focus more on the ones that could deliver a larger payoff will not get you more sales in the end.  To get more sales, you will have to upload more images that meet the needs of buyers.  Every time you're about to hit Upload on any given site, stop and ask yourself these questions:

Who will buy this?  What will it communicate for the buyer?  What goal does it help the buyer achieve?

If you can't quickly come up with a crystal clear answer to these questions, chances are you will see few if any sales for your new images. 

I hope this doesn't discourage you, or anyone else who reads it.  I'm just trying to offer helpful advice to anyone who has "hit the wall" or is not getting the desired ROI on their time spent in microstock.   The buyers are out there.  There are more than ever before.  The pie is growing, even though your slice of it may be shrinking.  Carve yourself a larger piece by doing a better job than your competitors at figuring out what buyers really want. 

Good luck!

In another thread, Lisafx mentioned that 90% of her income came from the top 4 sites. I think for most of us that's roughly true. So while you can add a trickle to your income from the smaller sites, it really doesn't make a ton of difference to your totals.

Before I became exclusive I switched some of the low-earner sites to an intermittent upload status - every 3 to 6 months I'd catch them up with recent stuff in my portfolio.

I think the advice to focus on what sells - at the big 4 - is good.

new members at MSG everyday and with cool nicknames!

Unequivocally yes. Better spending time creating than uploading.

For me IS is one of these low earners. Uploading is so cumbersome that I was able to have 200 images in 2.5 years. I got only one image that got more than 1DL/m :-) At SS I got few dosens which had 2DL/m. So I guess I am not doing very well :-(

My top five sellers at IS are 24.2  16.3   8.8  7.7  and 5.9 dls/month.

I'm at     10.3     9.0     5.4     4.5     2.7 

My top five sellers at IS are 24.2  16.3   8.8  7.7  and 5.9 dls/month.

Lou, are any of top sellers landscapes?

another thread, Lisafx mentioned that 90% of her income came from the top 4 sites. I think for most of us that's roughly true. So while you can add a trickle to your income from the smaller sites, it really doesn't make a ton of difference to your totals

thanx jsnover, I saw lisa's post just after I posted and it does answer the question.... So I am gonna focus on the big four and do the others when I can, have time, feel like it, am bored

Man, your guys rock with downloads per month!! Inspirational to see
I'm at 1.5   1.5  1.2  1.1 and a whopping 1 
My "best seller" is a landscape, so yeah...go figure

1.3  1.3  1.1  1.0  1.0

Now I don't feel quite so bad.

9.6 3.4 3.0 2.8 2.5

Good to know there are people with worse results than me.   

shame on you!! eheh

WOW!  had no idea all that was there.
New Toy!

Haven't been w/iStock long enough to have anything meaningful, but do appreciate the info.  Thanks.