Let me start by saying Im a complete noob, so forgive me if what Im writing sounds retarded, but it seems logical to me from what knowledge I have from watching VODs.
Since I dont have a beta key and the current AI is pretty bad, I started doing random little tests on damage, how many shots it takes to kill what, etc. and I started testing the optimal number of drones for harvesting. I found a couple of things out, the more obvious of which is that mineral nodes which are closest to your HQ can support only 2 harvesters whereas the ones that are a space farther can support 3 with each worker being slightly less efficient as a result of the timing. So optimal saturation should be 2xclose nodes + 3xfarnodes which is usually 21 or 20. You can put more on, but beyond this point the mining rate of your worker will drop approximately 20 fold.
I figured I would try some tests to figure out the average income with various HQ positions in combination with certain numbers of harvesters. Long story short I found that placing an expo 1 space farther away from the minerals actually allows you to mine out a mineral field more quickly at full saturation for an increase of only 3 workers. The downside is obviously that your workers have to travel slightly longer to return home with their cargo, meaning that before you approach the saturation point you will be making less than you would with normal placement, making it pretty impractical for early expos.
I realized though that it could be applied to high yield expos in mid/late- game for a couple of reasons. First, the high yield fields dont have as many nodes as the normal ones, meaning the number of workers needed for full saturation will drop by around 6. Second, by the time youre expoing at the high yield you should have enough workers to fully saturate the nodes immediately when the HQ finishes, skipping the part of the curve where you would be mining more slowly than an HQ placed 1 square closer. Finally, because the high yields offer double minerals the disparity between the average intake of the differently placed HQs is also doubled accordingly.
So if you get a high-yield expo up, place it 1 space farther from the nodes than you normally would, and immediately saturate it with 18 workers, you will be able to mine it out a few minutes faster than someone with a properly placed HQ.
You can obviously test this really easily yourselves, but here are the basic numbers I came up with for anyone who is too lazy. Im assuming that the income counter on replays is measured in units per minute:
1 worker mining at minimum proximity can collect around 40.5 resources per minute (gas and minerals mine at the same rate)
2 workers mining any node will acquire fully double what one would, but if a node 1 space farther is given a third worker, this third worker will increase your MPM(minerals per minute) by roughly 30 instead of 40, because there is a brief period of waiting for the previous worker to finish.Dancing workers (a third worker on a proximity node) only increase your tally by roughly 2.5 MPM, after which point the increases get exponentially smaller.