In the seventeenth and eighteenth centuries, the British parliament enacted a number of laws, called Navigation Acts, governing commerce between Britain and its overseas colonies. For example, the Navigation Acts of 1660 and 1663 barred the empire’s colonial merchants from exporting such commodities as sugar and tobacco anywhere except to England and from importing goods in non-English ships. Similarly, the Molasses Act of 1733 taxed all foreign molasses (a thick liquid drained from sugarcane and used to make rum) entering the mainland American colonies at sixpence per gallon. This act was intended less to raise revenue than to serve as a protective tariff (tax) that would benefit British West Indian sugar producers at the expense of their French rivals. By 1750 a long series of Navigation Acts were in force, with several effects on the North American colonial economy.

For one thing, the laws limited all imperial trade to British ships, defined as those with British ownership and crews that were three-quarters British. For purposes of the legislation, Parliament classified all colonists as British. This restriction not only contributed to Great Britain’s rise as Europe’s foremost shipping nation but also laid the foundations for an American shipbuilding industry and merchant marine. By the 1750s one-third of all imperial vessels were American-owned, mostly by merchants in the northeast and in mid-Atlantic colonies. The swift growth of this merchant marine diversified the northern colonial economy and made it more self-sufficient. The expansion of colonial shipping in turn accelerated urbanization by creating a need for centralized docks, warehouses, and repair shops in the colonies. By 1770 Philadelphia and New York City had emerged as two of the British Empire’s busiest ports.

The Navigation Acts also barred the export of certain “enumerated goods” to foreign nations unless those items first passed through England or Scotland. The American mainland’s chief items of this sort were tobacco, rice, furs, indigo (a Carolina plant that produced a blue dye), and naval supplies (such as masts and tar). Parliament never restricted grain, livestock, fish, lumber, or rum, which altogether made up 60 percent of American colonial exports. Furthermore, Anglo-American exporters of tobacco and rice—the chief commodities affected by enumeration—had their burdens reduced by two significant concessions. First, Parliament gave tobacco growers a monopoly over the British market by excluding foreign tobacco, even though this hurt British consumers. (Rice planters enjoyed a natural monopoly because they had no competitors.) Second, Parliament tried to minimize the added cost of landing tobacco and rice in Britain (where customs officials collected duties on both) by refunding the duties on all tobacco and rice that the colonists later shipped to other countries.

The navigation system’s impact on the colonies encouraged economic diversification as well. Parliament used British tax money to pay modest incentives to Americans producing such items as silk, iron, dyes, hemp, and lumber, which Britain would otherwise have had to import from other countries, and it raised the price of commercial rivals’ imports by imposing protective tariffs on them. The trade laws did prohibit Anglo-Americans from competing with large-scale British manufacturing of certain products, most notably clothing. However, colonial tailors, hatters, and other small clothes manufacturers could continue to make any item of dress in their households or small shops. Manufactured by low-paid labor, British clothing imports generally undersold whatever the colonists could have produced given their higher labor costs. The colonists were also free to produce iron and built numerous ironworks.

Finally, the Navigation Acts made the colonies a protected market for low-priced consumer goods and other exports from Britain. Steady overseas demand for colonial products created a prosperity that enabled colonists to consume ever-larger amounts not only of clothing but of dishware, home furnishings, tea, and a range of other items both produced in Britain and imported by British and colonial merchants from elsewhere. Consequently, the share of British exports sold to the colonies rapidly increased from just 5 percent in 1700 to almost 40 percent by 1760. Cheap imported goods enabled many colonists to adopt a lifestyle similar to that of middle-class Britons.

在十七世纪和十八世纪，英国议会出台了一系列法律，称为《航海条例》，以管理英国与其海外殖民地之间的贸易。例如，1660年和1663年的《航海条例》禁止帝国的殖民商人向除英格兰以外的任何地方出口诸如糖和烟草等商品，以及用非英国船只进口商品。同样，1733年出台的《糖蜜法》向所有的外国糖蜜征税（这是一种从甘蔗中提取出来的，用来制造朗姆酒的浓稠液体。）以每加仑六便士向进入美国大陆殖民地的糖蜜征税。这项法案的目的不是为了增加收入，而是作为一种保护关税（税收），以牺牲法国竞争对手的利益为代价，让英国西印度的食糖生产商受益。到1750年，一系列《航海条例》的生效，对北美殖民地经济的发展产生了一些影响。 首先，法律将所有帝国贸易都限制为英国船只，这些英国船舶必须是英国拥有所有权，且英国船员占到总数的四分之三。为了达到立法的目的，议会将所有殖民者归为英国人。这一限制不仅有助于英国崛起为欧洲最重要的航运国，而且为美国造船业和商船的发展奠定了基础。到十八世纪五十年代，所有帝国船只中有三分之一是美国人拥有的，大部分为东北部殖民地和大西洋中部殖民地的商人所有。这个商船的迅速发展使北部殖民的经济变得多元化，并使该殖民地变得更加自给自足了。殖民地航运的扩张反过来又加速了城市化进程，因此需要在殖民地建立中央码头，仓库和修理厂。到1770年，费城和纽约市已成为大英帝国最繁忙的两个港口。 《航海条例》还禁止将某些“查点的货物”出口到外国，除非这些物品先通过英格兰或苏格兰。美国大陆上的这类产品主要包括烟草，大米，毛皮，靛蓝（一种卡罗莱纳州植物，可以产生蓝色的染料）以及海军物资（如桅杆和焦油）。议会从未限制粮食，牲畜，鱼类，木材或朗姆酒的出口，这些物质共占美国殖民出口的60％。此外，英美烟草和大米出口商 - 受查点影响的两种主要商品 – 通过做出两项重大让步，减轻了其负担。首先，议会通过拒绝外国烟草的进口，尽管这伤害了英国消费者，但是可以让烟草种植者垄断英国市场，（稻米种植者因为没有竞争对手而享有自然垄断权。）其次，议会试图通过退还所有殖民者之后运往其他国家的烟草和大米关税（在海关官员向这两种商品都征收关税）来降低英国种植烟草和大米的额外成本。 航海体系对殖民地所产生的影响也促进了经济的多样化。议会利用英国的税收收入，来向生产丝绸，铁，染料，大麻和木材等产品的美国人提供适度的奖励，否则英国将不得不从其他国家进口这些产品，并通过对其征收保护关税来提高商业竞争对手进口商品的价格。贸易法明确禁止英裔美国人与制造某些产品的英国制造商产生大规模竞争，尤其是服装方面。然而，殖民裁缝，帽匠和其他小件服装制造商可以继续在家中或小商店制作任何衣服。由于劳动力价格便宜，因而英国服装的出售价格一般低于殖民者在劳动力成本上涨时可能生产出的任何产品的价格。殖民者也可以自由生产铁，因而他们建立了许多铁厂。 最后，《航海条例》使得殖民地成为廉价消费品和英国出口的其他商品的保护市场。海外对殖民地产品的稳定需求创造了经济的繁荣，这使得殖民者消费了越来越多钱，不仅用于购买服装，而且还用于购买餐具，家具，茶叶以及一系列在英国生产并由英国殖民地商人从其他地方进口而来的其他物品。因此，英国出口到殖民地的出口份额迅速从1700年的5％增加到了1760年的近40％。便宜的进口商品使得许多殖民者可以过上一种类似于英国中产阶级的生活方式。