Here, for example, is a posting from the SECRECY REPORT CARD 2005 illustrating the changing trends in the the classification and de-classification of U.S. government data. (You can probably guess the direction of the curves.)
Spotlight What is the US Government Not Telling Us?
Source: SECRECY REPORT CARD 2005
The number of classified documents is steadily increasing, while the number of pages being declassified is dwindling. This data were uploaded by mcroydon.