The growing cost is largely due to the number of new classified documents added each year. After peaking at half a million new documents a year at the end of the Cold War (in 1991) new additions declined to 105,263 by 1996. Then it began climbing again, and peaked once more in 2004 at 351,150 documents. Since then it has been declining. But there are still about 200,000 new documents added each year. There is also increase in "derivative classification" (reconfigured classified data, as in bits of older classified documents combined into new docs). This has been rising even faster. There were 5.6 million such actions in 1996, and 22 million by 2007. That's another reason to declassify old documents, to reduce these "derivative" documents. But declassification is a low priority activity, and government security officials are not enthusiastic about declassification, mainly because there's always the risk of declassifying a document that later turns out should have stayed secret.

Attempts to reduce the number of secret documents rely on creating fewer new classified documents and declassifying more old stuff. More data is now being classified as "material that will automatically declassify in ten years" (easy to do with a lot of technical or operational data). Since 1980, 1.5 billion pages of classified documents have been declassified. That number has been increasing lately because an individual document can contain hundreds of pages. The declassification effort is not fast enough, as the body of classified data (whose actual size is classified) continues to grow, as does the expense to protect it from unauthorized eyes.