同比一般情况下是本年第n月与过去某年的第n月比。常见的英文表达有以下5种：

· from the same period

· compared to the previous year

· from a year earlier

· year-on-year

· year-over-year

e.g. The median household income in the third quarter of 2002 fell from $18,000 in the same period from the year before to $16,100, representing a fall of 10.6%.

去年第三季的家庭住户每月入息中位数数字，已由前一年同期的18,000元下降至16,100元，下跌幅度为10.6%。

During 2010, the visits to the WHC website increased by 22.4% as compared to the previous year.

与此前一年相比，2010年间，世界遗产委员会网站的访问量增长了22.4%。

Another significant development was the further reduction in long-term unemployment (i.e. duration of six months or longer). In the third quarter of 2007, this number fell to 34 700, representing a drop of more than 10 000 persons or 23.5% from a year earlier.

另一项重要的发展是长期失业(即失业达六个月或以上)人数进一步下降；这项数字在二零零七年第三季跌至34,700人，较一 年前同期减少10,000人以上或23.5%，此跌幅较总失业人数同期的12.0%跌幅更大。

The number of civil cases heard in the Supreme People's Court grew 40% year-on-year to over 40,000, with the average case lasting only 172 days.

最高人民法院审理的民事案件的数量每年持续增长40％，一年超过40,000，平均每个案件大约持续172天。

The hotel sector experienced the next highest level of growth in employment, with employment levels rising from 2,965 in 2007 to 3,046 in 2008, representing an increase of 81 jobs and growth of 2.7 per cent year over year.

旅馆业的就业人数从 2007 年的 2,965 人增加为 2008 年的 3,046 人，比前年增加 81 个就业机会，或增长 2.7%。