李嘉图经济学

李嘉图出生于1772年，后来靠做证券经纪人和贷款经纪人致富。 在27岁时，他读了亚当斯密的《国富论》，并被当中的经济学原理所激发。他的主要经济学思想都集中在1817年出版的政治经济学和税收原理当中。这本书提出了一系列的理论，他们后来成了马克思的《资本论》和马歇尔主义经济学共同的理论基础。这里所讲的理论，包括地产（土地）收益理论、价值的劳工理论以及最重要的比较优势理论. 
李嘉图在读过亚当斯密后十年写了他的第一篇经济学文章，最终这篇"金条之争"凭借其关于19世纪英格兰通货膨胀的理论而为李嘉图在经济学界树立了名声。这个理论后来被称为货币主义,主要内容是过度的货币量导致通货膨胀。 李嘉图也为古典经济学的创建做出了巨大贡献， 因为他积极为不受政府法律或壁垒限制的自由贸易 和 自由竞争摇旗呐喊。
边际报酬递减.
另一个让李嘉图出名的概念出自他的"关于玉米低价格对于股票收益影响的随笔"，这就是著名的边际效应递减法则 (李嘉图, 经济学随笔, Henderson 826).所谓的边际效应递减法则说的是如果对一个生产要素提供更多的数量而对另外一个生产要素保持数量不变，则总产量created by the extra units will eventually get smaller to a point where overall output will begin to fall ("Diminishing Returns").
举一个例子，考虑一个只有两资源--劳力和土地的简单农场。假设该农场有一百亩土地及一名工人(劳力资源)。这个地-工组合可达到一定程度的产出。 如果我们增加土地且劳动力不变，该工人对每亩地的照料程度就会下降(假设其他条件皆不变)。所以，产出可能会增加，但单位土地的产量可能下降。如果我们继续增加该名工人须照料的土地，最终会因土地过剩而导致工人分身乏术，总产量开始下滑(及分配给各亩田的劳动时数减少) 。这就是典型的边际效应。 This is the typical stylized result of increasing one productive input while holding the others constant (versus increasing all inputs, generating economies of scale).
比较优势.
李嘉图反对关税以及其他对于国际贸易的限制. 李嘉图发展了著名的比较优势理论 (Henderson 827, Fesfeld 325). 根据华盛顿国际贸易理事会的定义，比较优势是指相对于其他国家，某国能够以相对于其他商品较低的价格生产某种商品。在"经济学原理"一书中, 李嘉图表示，比较优势是一种specialization technique used to create more efficient production (52) and describes opportunity cost between producers (53). With perfect competition [https://web.archive.org/web/20061129125355/http://www.uncc.edu/hscampbe/landuse/e-support/Glossary.html] and undistorted markets, countries tend to export goods in which they have a comparative advantage ("Comparative Advantage"). 
在举一个例子，设想两个国家同时生产卡片和pencils，并且使用同样的时间生产一份产品（见表格）. 国家甲can make 4 pencils if they specialize just in pencils at the expense of one card, but this country can also make ¼ of a card at the expense of one pencil. 同样的逻辑适用于国家乙: 如果国家乙makes only pencils, it will make 2 pencils at the expense of 1 card.。如果国家乙specializes only in cards, it will make ½ of a card at the expense of a pencil. 比如，,国家甲在pencils上面相对于国家乙有比较优势(4 pencils to 2 pencils), 然而国家乙在cards上相对于国家甲有比较优势(½ of a card to ¼ of a card). 在李嘉图的比较优势的概念中，这两个国家应该专注于他们能够做的更好的行业。根据"经济学财富百科全书"的说法，李嘉图的比较优势理论是"今天大多数经济学家信奉自由贸易的主要理论基础" (827). 
李嘉图经济学今日的应用.
尽管大卫·李嘉图是19世纪人物， 很多人在日常经济学中仍然在引用他的工作成果，例如地租理论。李嘉图的地租理论主要包括农民和地主的农业模式。由于高生产力的土地能够生产更多的农作物，市场将支付相同价额购买有利和不利的土地上种植的作物，农民愿意付出更多钱来买高生产力的土地来种植更多的作物挣钱（Henderson 827).
李嘉图也有另一个有影响力的理论：最低工资。他知道如果人口产生较大幅度的增长，就业需求就会增加，工资将会降低到无法养活人们的水平，因为许多人会愿意接受低薪工作来维持生存（圣克莱尔9，Fusfeld 325）。这种对最低工资工作的观察在今天尤其相关，特别是在关于最低工资法实施的争议中。在他的著作"政治经济学和税收原理"中，李嘉图提到我们更看重的工作，其薪酬会比我们不太重视的工作要高。
对李嘉图而言，价值和生产成本有很大关系，后者包括工资和利润 (St. Clair 27) ，你支付多少钱给工人会影响产品的价格。他还认为，产品的价值与生产所需的劳动品质有关。(Principles of Political 5) 举例来说，如果一件商品是手工制作，而不是工业制造的话，那么支付的价格就会稍微高一点。虽然这是正确的，但李嘉图也认为在销售物品时，应该考虑到劳动力或机器本身，而且每一件物品的价格都应该包含一点劳动力的因素。(St. Claire 24) 李嘉图讨论了我们今天的经济世界所面临的许多问题，如最低工资和租金(Fusfeld 325)，这些问题在今天或许和 19 世纪一样重要，这也是大卫·李嘉图的经济理论仍然是现代经济学重要组成部分的原因。
引文.
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