Government agencies don't have to disclose specific numbers of FOIA requests, there are a few key aspects of the Freedom of Information Act (FOIA) and broader legal principles that contribute to this practice:

1. FOIA Exemptions:

The FOIA itself contains nine exemptions that allow agencies to withhold certain information from disclosure. While these exemptions primarily focus on protecting sensitive information like national security secrets, personal privacy, and law enforcement investigations, some legal interpretations extend them to encompass internal agency data and statistics.

2. Privacy Act of 1974:

This act restricts the disclosure of personally identifiable information (PII) held by federal agencies. While the number of FOIA requests itself might not contain PII, arguments can be made that disclosing them could reveal trends or patterns potentially leading to the identification of individuals involved in submitting requests, particularly in smaller agencies or specific regions.

3. Security Concerns:

Disclosing the volume of FOIA requests could potentially expose vulnerabilities in agencies' FOIA processing systems or reveal areas of high public interest, which could be exploited for malicious purposes. This concern might be particularly relevant for agencies dealing with sensitive information or facing ongoing cyber threats.

4. Administrative Burden:

While transparency is a core principle of FOIA, responding to requests for detailed data on every FOIA request received and processed could create a significant administrative burden for agencies. This includes the time and resources needed to compile and analyze the data, potentially diverting resources from fulfilling actual FOIA requests.

It's important to note that these are not absolute rules, and there can be ongoing debate and litigation regarding the specific circumstances under which agencies can withhold data related to FOIA requests.