To be clear, Transparency International (TI) doesn't measure corruption. In the whole work you can see they develop all the investigation with the word "perception", which mean their work is to know what the common citizen feel about the government and their corruption's fight.
Having said that, China is going to keep dropping two more places before they can rise in the charter of TI. They're going to drop not because they're lacking of fighting corruption, but they are currently uncovering lots of corruption cases. This is not new. What the people are trying to tell is deeper, they demand a full political reform and the authorities are trying to respond. The statistics are talking about cases of corruption and the measures:
The number of cases is even before 2009, remember the Shanghai pension case for example. Jason Lyall wrote about the current measures:
The Chinese Communist Party is centralizing authority, broadcasting the self-criticisms of local officials and calling for a new morality in public life. The party’s decentralized and technocratic rule is over, replaced with a new, more political mode of governance aimed at better controlling local officials.
What people see is the response of their authorities and the opposition inside the China Communist Party says the efforts made by them are not enough, giving the reason in some terms to TI, that's why the result you found. Foreign Policy made a post about the cases of corruption, considering the report made by the Discipline Committee:
You may think about the procedures and the partiality of the justice in the country and we have to take in consideration the number of cases keep growing while several cases are treated. These changes started (precisely highly supported) with Xi Jingping are going to take lots of time, but the message sent inside the Communist Party is very clear as the FP said:
To finish, I would recommend this paper to understand the beginning of the corruption fighting in 2000s of Zengke He.