Quote from: GooberGoo on July 03, 2011, 11:53:08 AM

For the lay person, can you explain "zero-variance" again in real-dollar terms?

For example, we all know the difficulty now is 1,379,223, which currently yields and approx of .73 BTC / day, 22.17 BTC a month

and is set to go up to 1,571,848 which will yield less.

The question then is, as difficulty goes up, safe to assume that the yield in BTC will decrease right?

Zero-variance payments mean you get the exact amount you would expect to earn on average. Using the current yield of .73 btc per day, you would get an amount equal to that daily rate every pay period. It's called zero variance because it's a fixed rate based on the difficulty, while if you mined on any pool you would have some lucky days and some unlucky days and would never be able to earn a fixed rate like this. Pools also have fees which would reduce the amount you earn.

If the difficulty does go up to 1,571,848 the 1ghash will be expected to pull in .64btc/day from then on. You would want to come up with a reasonable expectation on what you expect the future difficulty growth to be over the next year and decide if it's worth it for you. No one can say for sure what will happen, but it's pretty likely that difficulty will increase at a decent rate in the short term and will probably level out when mining becomes only marginally profitable. So I can't say exactly how many BTC this contract will produce over it's lifetime because anything could happen, but I expect it to earn somewhere between 100 and 250 BTC.