急急问CR JJ！！

The total market value of real estate in Altonville has steadily declined over the past four years.  This decline has meant that the overall figure on which the city’s property tax is based—the assessed value of that real estate—has also declined.  The percentage of assessed value that was paid as property taxes to the city, however, did not change from year to year during this period.

谁能帮忙翻译一下这个啊，觉得意思还是没搞懂。。。。

Real Estate的市场价值在过去四年里持续走低。同时导致了property tax的税基总量减少。而缴税的百分比（就是税率啦）没有变化。