求翻译：美国关税在1846～1860年间多次下降，平均税率由40%以上降到20%～30%之间，美国自1816年以来首次接近实现了自由贸易。而1861年为支付内战的必要费用而提高关税，又恢复了1846年的保护关税水平。是什么意思？

U.S. tariffs on many occasions between 1846 - 1860 decline, the average tax rate from 40% to 20% to 30%, and the United States since the first time since 1816 close to achieving free trade. The civil war in 1861 to pay the necessary fees and higher tariffs, but also restored the level of tariff prot

tariffs of the United States on several occasions in 1846 ~ 1860 years, the average tax rate dropped by more than 40 per cent to 20 per cent to 30 per cent since 1816 between the United States, since the first closer to achieving free trade. The 1861 civil war for the payment of the necessary costs

The American customs duty drops many times in during 1846~1860 years, the average tax rate falls from 40% above to 20%~30% between, US close has realized the free trade for the first time since 1816.But in 1861 enhanced the customs duty for the payment civil war essential expense, also restored 1846

United States tariffs between 1846-1860 down multiple times, between the average tax rate by more than 40% down to 20%~30%, United States since 1816 close to free trade for the first time. In 1861, raising tariffs for the payment of necessary expenses of the civil war, again the level of protective

Numerous decline within 1846-1860 years of American tariff, the tax rate drops to 20%-30% from 40% of the the above on average, U.S.A. has realized the free trade closely for the first time since 1816. And raised tariffs for paying the necessary expenses of the civil war in 1861 and resumed the prot