I paid Zakat on my wealth last year. However, there is no addition this year. Do I have to pay Zakat again this year on the same wealth for which I paid last year?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If the wealth you have equals the value of 85 grams of gold and it has been in your possession for the previous lunar year, then it is subject to zakah, i.e. you have to pay 2.5% of it every year unless its value becomes less than the value of 85 grams of gold.
Allah knows best