I posted 3+ year trends of RPI (return per image) statistics from my portfolio:
http://microstock.pixelsaway.com/return-per-image-rpi-from-my-microstock-portfolio-3-year-trends/

I am not sure if the overall picture is encouraging or discouraging.
IS is obviously going downhill (it would be worse without pictures+),
SS is going up, but still cannot catch IS. And, it's summer now.
Perhaps, it's time to shoot something for fun ...

Out of curiosity, why do you think IS RPI is slowly falling?

RPI is affected by

1 - number of sales (downloads) going down
     many threads on IS situations in this forum
         
2 - change in commission
     10% cut for 2011

3 - acceptance rate and upload limit
     more rejections during last year or so
     My RPI is based on a total number of pictures in my portfolio, not pictures accepted by IS.
     This factor really affects my RPI for DT ("too similar" rejections).
     I have a similar size portfolio with FT, but they don't reject my bestsellers like DT.

Nothing very surprising: IS is going downhill and SS up.

it shows also that "other agencies" play a "big" part too, making that time worth I guess (they represent 18% in my earnings beside the top5 agencies)

very nice blog post again, you have been doing a great job since day 1, congrats ON your success!

6 months later ...
I just posted an updated graph of RPI for my microstock portfolio covering 2009-2011 period:
http://microstock.pixelsaway.com/microstock-portfolio-return-per-image-rpi-2009-2011-trends/

Nothing very surprising: IS is going downhill and SS up.

Interesting graph and tracking data. I'm missing something so if you can answer I'd appreciate it, if you wish not, that's fine.

How many files on IS compared to SS? Or are they close?

Did I read that right, the RPI is under $1 per image, and that's for the total period of time 3.5 years or per year? Or?

I'd say its per month

Wow I'm in the wrong business. I should be shooting outdoor photos. "I have around 3400 pictures in my stock portfolio" so lets see, that's $2720 a month. and he's got them on four agencies... $10,880 a year? I need a canoe. 

my graph shows monthly RPI

unfortunately, outdoor pictures contribute just a very tiny fraction to my total sales, so no new canoe from microstock sales for me 

Kayak? 

Nice going, it does prove that quality pays more than "How many pictures does it take to make $x a month?"

My answer has always been pictures of what?

Your blog has always been entertaining reading since you started it, and the only one I know of (there might be others?) That has real numbers now hand waving, claims and percentages. Nice Work!

Oh and fudge my RPI is going down on Alamy again. I just uploaded a couple hundred new images... 

just read more carefully, and i see that yes, that is what it was.  so yea, hopefully the average line is showing the trend, not the monthly line.

then i noticed the dip was due to january.  then i noticed most other january's had a dip too.  then i noticed they werent NEAR as bad.  looks as if the extremes are getting more pronounced.  kinda like climate change!  WHERE IS AL GORE WHEN WE NEED HIM!?