天下沒有免費的午餐（There ain't no such thing as a free lunch.)，你想得到一樣?xùn)|西，必須失去一樣?xùn)|西。人們總會面臨權(quán)衡取舍（trade-offs)。
例如，我每晚上總共有4小時學(xué)習(xí)。如果我花3小時學(xué)英語，就意味者我失去了本可以用來學(xué)數(shù)學(xué)的3小時失去了。
Principle 2:
The Cost of Something Is What You Give Up to Get It
因為人們需要權(quán)衡（trade off), 所以在做決定之前往往會考慮當(dāng)中的代價和收益。
比如說，考慮是否要上大學(xué)，你就要考慮當(dāng)中的代價和收益。
代價：高額的食宿費、上學(xué)四年如果用來工作的話可能取得的收入.......
收益：提高自身的知識水平、終身獲得更好的就業(yè)機(jī)會。
Tecnical Term:
opportunity cost: whatever must be given up to obtain some item
Rational people know that decisions in life are rarely black and white but usually involve shades of grey.
Economist use the term marginal change to describe a small incremental adjustment to an existing plan of action.
Rational people often make decisions by comparing marginal benefits and marginal costs.
例如，一架200座的飛機(jī)的飛行成本是100,000美元，那么，每個座位的成本就是500美元。理論上，每張機(jī)票的售價應(yīng)大于或等于500美元。當(dāng)如果飛機(jī)上有10個座位沒坐滿，這時有一名額外的乘客只肯掏300美元買票，應(yīng)不應(yīng)該賣給他呢？答案是肯定的，因為這樣做收益大于成本。
An incentive is something that induces a person to act.
Many policies change the costs or benefits that people face and, therefore, alter their behaviors.
例如，油價漲了，開車的人就少了，搭公交的人就多了。
計劃經(jīng)濟(jì) VS 市場經(jīng)濟(jì)
亞當(dāng).斯密說，有一只看不見的手（invisible hand)引導(dǎo)著家庭和企業(yè)在市場中相互作用，然后取得理想的市場收益。市場經(jīng)濟(jì)（market economy）中那只看不見的手通過【價格】來指導(dǎo)經(jīng)濟(jì)活動。
Tecnical Term:
property rights: the ability of an individual to own and exercise control over scare resources
market failure: a situation in which a market left on its own fails to allocare resources efficiently
externality: the impact of one person's actions on the well-being of a bystander
market power: the ability of a single economic actor to have a substantial influence on market prices.
政府在市場經(jīng)濟(jì)中也發(fā)揮著重要作用。如果沒有政府來維護(hù)市場秩序，市場經(jīng)濟(jì)就無法正常運作。
生產(chǎn)者的財產(chǎn)所有權(quán)（property rights）需要政府來保護(hù)。如我一個農(nóng)民的莊稼老是被偷，那他以后還會去種田嗎？
因為市場自身存在固有的缺陷（market failure），所以市場需要政府的宏觀調(diào)控。比如說某年豬肉的需求增加，大家看見賣豬肉有利可圖，就一哄而上地去養(yǎng)豬，導(dǎo)致大量的資源浪費在養(yǎng)豬上。最后供過于求，資源浪費。如果政府不插手管理，市場就亂了套。
造成market failure的另一原因是market power。比如說，鎮(zhèn)上人人都需要水，而只有一口井，那么井的主人就不受“看不見的手”用以調(diào)控經(jīng)濟(jì)的手段---競爭的限制，就會任意哄抬物價。
語言學(xué)習(xí)：
7trade sth off (against / for sth)
· to balance ten things or situations that are opposed to each other
· 權(quán)衡；平衡；使協(xié)調(diào):
?They were attempting to trade off inflation against unemployment.
他們正力求在通貨膨脹和失業(yè)之間進(jìn)行協(xié)調(diào)。
fast:to eat little or no food for a period of time, especially for religious or health reasons
· 節(jié)食；禁食；齋戒:
?Muslims fast during Ramadan.
伊斯蘭教徒在齋月期間齋戒。
induce:[VN to inf] (formal) to persuade or influence sb to do sth
· 勸說；誘使:
?Nothing would induce me to take the job.
沒有什么能誘使我接受這份工作。
orchard果園
skyrocket: to increase quickly to a very high level or amount
Costs/Sales have skyrocketed.
skyrocketing prices
His popularity skyrocketed after his latest movie.
brethren: people who are part of the same society as yourself
· 同一組織等的成員；同道；同仁:
?We should do all we can to help our less fortunate brethren.
我們應(yīng)當(dāng)盡力幫助那些不幸的兄弟姐妹。
prevail:~ (against / over sb) (formal) to defeat an opponent, especially after a long struggle
· (尤指長時間斗爭后)戰(zhàn)勝,挫敗
flag:to become tired, weaker or less enthusiastic
· 疲乏；變?nèi)酰粺崆樗p:
?It had been a long day and the children were beginning to flag.
這一天真漫長,孩子們都累得打起蔫來。
?Her confidence had never flagged.
她的信心從未減弱。
?flagging support / enthusiasm
fluctuate: ~ (between A and B) to change frequently in size, amount, quality, etc., especially from one extreme to another
· (大小、數(shù)量、質(zhì)量等)波動；(在…之間)起伏不定
【SYN】 vary :
?fluctuating prices
波動的價格
?During the crisis, oil prices fluctuated between $20 and $40 a barrel.
在危機(jī)時期,每桶石油價格在 20 元至 40 元之間波動。
?Temperatures can fluctuate by as much as 10 degrees.
溫差可達(dá) 10 度之多。
?My mood seems to fluctuate from day to day.
我的情緒似乎天天在變。
ominipotent=omini(=all)+potent
