01 The most pervasive prediction market tool is "futures market." 预言市场的工具早就存在，也就是行之有年的期货市场
Blockchain developers favor topics on prediction markets very much. There are already some projects listed on exchanges, such as Gnosis, Augur...etc.
前一阵子广受区块链技术开发者追捧的一个主题是“预言市场”，相关的项目有Gnosis, Augur...等。
I would like to give a brief analysis on whether prediction market tools can be disruptive innovation for our future or not, and whether these projects are good investments.
预言市场是什么？预言市场导入区块链技术的必要性在哪里？本篇文章主要想分析这类型项目的意义到底在哪里，以及预言市场工具是否具备投资的价值。
Actually, the concept of prediction market has long been known by people, which is the existence of "futures market". The public often have misunderstanding about futures market, perceiving this tool as purely speculative due to its highly leveraged and highly uncertain characteristics.
其实预言市场的工具在我们生活中早已普遍存在，最常见的就是期货市场。
期货市场对经济体系起到什么影响？很多人认为期货是一个类似赌博的经济活动：高度杠杆、获利的可能性高度随机，是一种纯粹的投机行为，不涉及实质的生产活动。
To clarify this misunderstanding, you have to know the initiative of the innovation of futures. At first, futures got the same function as insurance. People buy futures contract to give themselves a protection from uncertainty. Regardless of whether the markets goes up or down, they can always keep their future cashflow fixed.
For example, electronic car companies such as Tesla might have the need for aluminum futures because the core material of its production is aluminum, and Tesla wouldn't be happy to see their raw material cost fluctuate too much with the market.
这种看法完全误解了期货的作用。事实上，期货市场满足了人们对“确定性“的需求。
期货的初始意义就像保险，有一些人购买期货，买的是“未来固定的现金流”，也就是说，不管未来发生什么情况，我都能够维持固定的收入或支出。
举例来说，特斯拉为了避免他的生产成本波动过大，会产生购买铝原物料期货的需求，以维持他未来每一批量生产，成本都是固定的，不会受到铝市场价格的影响。
生产者有固定原物料价格的需求，但是谁来满足他的需求呢？为什么会有人愿意跟生产者对赌，拥抱这样的不确定性呢？
02 Futures market enables more specific expressions about future economic event 期货的本质，是让交易者表达对未来的不同看法
It's common that people share different opinions on future events, and the futures market provides a platform for people to act on their opinion and make profits.
The futures market wouldn't exist if people share the same expectation about the future. In other words, as long as there is disagreement, there is a futures market.
人们对于未来事件往往会抱持不同的看法。当人们对未来的看法出现歧异时，他们就可以透过期货市场来表达他们的看法，进而获取利益。期货市场的根基在于未来的不确定性，当日子一天一天到来，我们对于眼前的未来有更高的确定性时，期货的可操作性就会下降。
所以，只要有意见分歧、对风险有不同的态度，交换就会存在，但你要找到一个愿意跟你交换的人，往往需要耗费大量的时间精力。市场，就是为了减少这样的摩擦力而存在的。市场为人们创造一个交换的平台、制定标准化的合约，促进交换行为产生，提高流动性。
03 What composites a futures contract 期货合约的组成
A standard futures contract involve three main parties: buyer, seller, and the intermediary (which is often the exchange. ) The intermediary takes the responsibility of ensuring the execution of the contract despite any default from the buyer or the seller.
一份期货合约的当事人包括三个主体：买方、卖方、中介。中介的作用在于促进期货市场的流通性，有了一个中间人，买卖双方都免除了对方不能履行合约的风险，因为期货市场具有不管发生什么事情，它都必须履行单边合约的信誉。
看到了吗？区块链最核心的价值出现了：信用。现在各国都有中心化的期货交易所，负责担保合约的执行。
04 How prediction market works？ 预测市场是如何运作的？
Participants in the market may choose to buy or sell contracts in which the provisions of profit/loss is conditioned on future events. The price of a contract could be calculated as the expected value of that future event.
预测市场是透过市场机制让参与者买卖未来事件的合约，其报酬由该事件的结果决定。因此，合约的价格可视为整体市场对该事件发生机率的预测。每个合约都会事先设定"到期日“，合约到期时，就可以确定该事件是”发生“还是”未发生“。若发生，则该合约的交易价格为一固定金额（假设为$100)；若未发生，则该合约的交易价格为0。
For example, if I buy a contract predicting the result of US presidential election, I can get rewards if I bet on Trump's winning.
举例来说，我在大选前发起了一个预测合约，找来了支持民主党和共和党的选民，来预测美国总统大选的结果，那些选了川普的人，在事后获得了回报。
All results are automatically executed by smart contracts. 在区块链的预测市场中，所有的合约都透过智能合约来完成。
05 The pros and cons of a prediction market 预测市场的利与弊
Pros <利>
A prediction market, in essence, is a vehicle for aggregating information about the expected outcome of a future event.
The advocates of prediction market believe that, highly liquid prediction markets are remarkably accurate in assessing the likelihood of future events. Probability drawn from these markets can effectively approximate more sophisticated actuarial estimates that require highly specialized training.
市场价格代表着相关资讯的汇总。之所以期货市场对天气的预测比气象局要准确，是因为对期货市场的当事人而言，钱都在里面，利益更加攸关啊！当事人一定会花更多心力希望能做出更准确的预测。良好运作的预测市场可以更即时地反映新的讯息，以协助人们做出判断。
Cons <弊>
If you bet on independent events which are uncorrelated to you behavior, you will try hard to do research and analysis because you are a stakeholder of this event and you want to be more accurate on your prediction .
Instead, if you can make a future event happen or not happen, you can manipulate the result and make profits on the result. Imagine you initiate a contract gambling whether a terrorist attack could happen to a certain area, the most likely consequence is that you attract terrorists to attack this area.
道德风险：在预测市场中，人们下注、博弈， 以利益绑定的形式来保证数据的准确性。
如果你下注的事件是独立、不相关的事，你虽然无法透过个人的行动改变整体事件的结果，比如气象，比如选举，但因为你利益攸关，会倾更多的心力去预测，也会吸引有专业能力的人加入这个市场，协助做出更准确的预测。
但，假想一下如果今天预测市场预测的是恐怖攻击呢？会发生什么结果？因为恐怖攻击完全是基于人的主观行为，恐怖分子可以投注这个市场，然后发动恐怖攻击，使他们收益倍增。
05 Projects comparison 预测市场项目比较
The decision arbitrary lies on REP token holders, which has nature limitations as long as the business scales up.
Augur 的事件仲裁机制是由REP持币者共同投票决定的，REP持币者等于是Augur平台的维护者。或许在早期，这机制是可行的，但ㄧ旦合约数量规模化后，普通人力是决不可能负担这些。
Gnosis uses a default centralized intermediary to determine the results.
Gnosis 使用ㄧ个默认的中心化信息中介(Oracle)来判定预测事件的结果。优点是能够将预测事件的判定自动化，提升运作效率。
至于中心化的各种为外界诟病的就不用多说了（包含服务器崩溃、数据被窜改等）。
Bodhi apples both a centralized intermediary and a final arbitrary right by BOT toke holders.
Bodhi 自称结合了Augur和Gnosis的优点，致力于创建新ㄧ代预测市场平台。不过它的事件结果也是由第三方信息中介(Oracle)判定，比较不同的是，当信息中介失效或错误时，Bodhi代币持有者可行使投票权，进行最终裁决。
Gnosis creates two types of token: GNO and WIZ. WIZ is pegged to $1 USD. WIZ can only be created via activating the utility of Gnosis tokens (GNO) and can be used to pay platform fees.
The total amount of GNO is fixed. GNO is the generator for WIZ. By "locking" GNO tokens, users can receive certain amount of WIZ (which is run by smart contract). Once users execute the contract, 30% of their WIZ will be distributed for immediate use, and the remaining 70% will be distributed proportionally over the locked duration.
在代币设计上，Gnosis创建了WIZ币作为交易费用，WIZ币和美元挂钩，ㄧ单位WIZ锚定1 USD。GNO代币持有者锁定代币，并获配WIZ。
Bodhi的代币叫BOT, Bodhi平台允许用户使用BOT和QTUM币参与押注，并预计未来开放所有代币都能进行押注。
我认为平台若运行成功，代币本身是有价值的，因为代币本身就是赌本，要押注就要持有代币。
但究竟哪个平台可以成功还不得而知，而且预测市场平台要成功还须仰赖网络效应，也就是越多人参与进来、黏着度越高，平台的预测准确度越高。
06 预言市场工具从科学的角度该如何实现？
Every prediction tool can be rooted back in data science and statistics. The most ideal way is the use of “ base rate”. In probability and statistics, base rate generally refers to the (base) class probabilities unconditioned on featural evidence, frequently also known as prior probabilities.
虽然从个体角度来看变异很大，从整体角度预测却是可行的，在决策科学中有一个很重要的概念，叫做基础比率，基础比率指的是以前的人做同样的事，做到的平均水平。预测未来最好的参考指标，就是基础比率。
人们透过投票预测，本质上就是调用自身过往的经验，来判断未来的走势。
07 小結
Business in such area is highly supervised and regulated because of the potential suspicion about market manipulation.
预测市场受到高度监管，也不太被大多数人认同，就是因为前面讲的，可能产生道德风险的缘故。
In insurance industry, insurers will do the investigation before they sign the contracts with the insured.
道德风险该如何避免？在传统保险市场可透过严格的核保制度来防范，也就是事前的审查机制，这往往须依靠受信任的中介来执行。
But in a decentralized world, there should be coding written to filter out unethical and illegal contracts.
在去中心化的世界，具有道德风险的合约应该要被制止。大部分白皮书并没有针对这层风险提出说明，而Delphy 白皮书提出了”事件过滤器”机制，用户创建好的event 会进入ㄧ个临时的event pool，系统同时会有ㄧ个event filter, 用来对违法的事件（比如对某国领导人的暗杀、恐攻...等）进行过滤。可惜的是，Delphy对于event filter的运作机制并没有更深一层的说明。
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