Proportional Token Allocation aka Proportional Refund approach

https://github.com/ethereum/EIPs/issues/642

https://medium.com/@nickikwhite_5051/token-sale-models-part-iii-proportional-refund-1243cbd43286

“In a proportional refund, the total number of tokens being sold is given up front as well as the total amount of money being raised. This sets a “cap” in a sense, but the difference is that the total amount of money that can be pledged to the ICO is allowed to exceed this cap. The token sale goes on taking in as much money as investors are willing to commit, very much like an uncapped sale, until the sale ends. At the end of the sale, the sold tokens are distributed according to the proportion of money invested by each participant and all excess contributions are refunded. So as an example, if 2 investors placed 300 ETH and 100 ETH in my token sale that was capped at 100 ETH, 75% of the tokens for sale would go to the first investor and 25% would go to the second. Then, 225 ETH would be refunded to the first investor and 75 ETH would be refunded to the second investor.

The nice part of this design is that you get the benefits of both a capped and uncapped sale. As in an uncapped sale, anyone can contribute to the sale and get a piece of the pie. And like in a capped sale, investors know the price at which they are buying the tokens, even if they may not know how many tokens they will end up getting. This sounds good on the surface, but it still doesn’t resolve the issue of being excluded from the sale by big players. Certainly you will always be able to contribute to the sale and get at least a small fraction of the tokens sold, but if a few whales put up 95% of the total ETH in the sale, then only 5% will go to the smaller players. And there’s nothing stopping a whale from majorly over allocating to the sale just to push other players out.”