From the whitepaper:
https://github.com/AntShares/AntShares/wiki/Whitepaper-1.1#kDistribution of Antshares
Before running the Genesis Block to create all the 100 million ANS, the Antshares team shall set certain rules on the distribution of these ANS.
Approximately 10% of the ANS have been designated to early supporters of the Antshares, in exchange of 600,000 yuan of seed fund. 400,000 yuan of the seed fund was from several individual investors under an overall valuation of 5 Million. 200,000 yuan of the seed fund was from a VC, PreAngel, under an overall valuation of 10 Million. It is worth noting that individual investors have contributed voluntarily in full-time or part-time.
Approximately 17% of the ANS have been designated to participants of the ICO Phase I, which took place in October, 2015, in exchange of 2,100 bitcoins. About 1,200 bitcoins were from individual investors while 900 bitcoins from one institutional investor.
Approximately 23% of the ANS will be designated to participants of the ICO Phase II, which is about to be launched in August, 2016. This ICO has no pre-set price or cap, but it does come with a refund mechanism. See details in the ICO CrowdFunding Draft.
All the remaining 50% of the ANS will be hold by the Antshares team. They will be locked for 1 year via a smart contract after the Antshares MainNet launch. After the 1-year locking, these ANS will be allocated for supporting the long-term operations of the Antshares.
ANS designated to early supporters, ICO 1 participants and ICO 2 participants will be in place after the official launch of the MainNet of the Antshares Blockchain. The MainNet is expected to be online in the 4th quarter of 2016.
The MainMet went live in October 2016 so the available supply is set to double in October. Chances are it'll slide until the devs make an announcememt as to what theyre going to do with 50million NEO.