两个词都对：
percent=百分数，percentage=百分点
从百分之一百增加到百分之一百零三，增加3 percent， 3 percentage。
从百分之一千增加到百分之一千零三十，也增加了3 percent， 但是30 percentage。

1、percentage (pər′sen•tij) 百分点，意思较窄。
(mathematics) The result obtained by taking a given percent of a given quantity.
2、per•cent also per cent (pər-sĕnt') 百分数，也可以做百分点解，意思较广。
adv.
Out of each hundred; per hundred.
n.
1. pl. percent also per cent. One part in a hundred: The report states that 42 percent of the alumni contributed to the endowment. Also called per centum. 百分数
2. pl. percents. A percentage or portion: She has invested a large percent of her salary. 百分点
3. percents Chiefly British. Public securities yielding interest at a specified percentage.



参考文献：http://www.answers.com/Percent?cat=technology