I realize this thread is over three weeks old, but I'm just catching up and wanted to add to what LastChance36 and Group9 had already stated.
From my perspective, Task Forces are generally either Agency/Department sponsored, or Initiative based. For example, Federal Agencies sponsoring Task Forces other than those already mentioned by Group9 include ATFE's Gang Task Forces, ICE's Border Task Forces, and USSS's Computer Crimes Task Forces; IRS-CI appears to be involved with most if not all of these Task Forces.
What I term Initiative based Task Forces would include: OCDETF (Organized Crime Drug Enforcement Task Forces), HIDTA (High Intensity Drug Trafficking Area Task Forces), and the ATTF (Anti-Terrorism Task Forces, as distinguished from the FBI sponsored JTTF's or Joint Terrorism Task Forces).
LastChance36's percentages regarding Agency participation (20 -25 %) appears to be reasonably accurate overall for most Federal Agencies.
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"When you have eliminated the impossible, whatever remains,
however improbable, must be the truth." Sir Arthur Conan Doyle