I don't think you will find it more fine-grained than by the Calendar year, It's reported yearly to congress.
I also don't think you will be able to match it too well to the 70 FBI cases because each warrant is rather specific and time limited, so there could be many of them for each case, or none for a case.
Some information below you may have already seen from the congressional joint intelligence investigation into 9/11. I had seen another quote implying that Ashcroft was cutting the FBI off from getting FISA warrants - Couldn't find it but I think it's in this same report somewhere.
From
http://www.gpoaccess.gov/serialset/creports/911.html"FBI Headquarters attorneys determined that there was not probable cause
to obtain a court order to search Moussaoui痴 belongings under the
Foreign Intelligence Surveillance Act (FISA). However, personnel at
FBI Headquarters, including the Radical Fundamentalist Unit and
the National Security Law Unit, as well as agents in the Minneapolis
field office, misunderstood the legal standard for obtaining an order
under FISA."
"12. Finding: During the summer of 2001, when the Intelligence Community was bracing for an imminent al-Qa段da attack, difficulties with FBI applications for Foreign Intelligence Surveillance Act (FISA) surveillance and the FISA process led to a diminished level of coverage of suspected al-Qa段da operatives in the United States. The effect of these difficulties was compounded by the perception that
spread among FBI personnel at Headquarters and the field offices that the FISA process was lengthy and fraught with peril.
Discussion: In the summer of 2000, during preparation for the trial in New York of those involved in the bombing of the U.S. embassies in East Africa, prosecutors discovered factual errors in applications for FISA orders sanctioning electronic surveillance. The FISA Court found that these errors included an erroneous statement that a FISA target was not under criminal investigation, erroneous statements concerning overlapping intelligence and criminal investigations, and unauthorized sharing of FISA information with criminal investigators and prosecutors.
The FISA Court also determined that these errors called into question the certifications that had been made by senior officials that the FISA surveillances requested by the applications had as their purpose the gathering of foreign intelligence, rather than criminal-related information, as required by FISA. After being informed of additional
errors in subsequent months, the FISA Court barred an FBI agent who had prepared one of the erroneous applications from appearing before the Court again.
The FBI and the Department of Justice痴 Office of Intelligence Policy and Review (OIPR) began a systematic review of the FISA application process in September 2000 to ensure the accuracy of FISA Court filings. Some FISA surveillances targeting al-Qa段da agents were allowed to expire while OIPR and the FBI investigated how the
errors had occurred. These orders were not renewed until after the attack on USS Cole in October 2000. In April 2001, the Bureau promulgated procedures for the review of draft FISA declarations and the submission of FISA applications to the Court. OIPR also
revised the standard al-Qa段da FISA application to reduce the amount of extraneous information that was required and that increased the likelihood of factual errors.
During this process, many FISA surveillances of suspected al-Qa段da agents expired because the FBI and OIPR were not willing to apply for application renewals when they were not completely confident of their accuracy. Most of the FISA orders targeting al-Qa段da that expired after March 2001 were not renewed before September 11.
The Joint Inquiry received inconsistent figures regarding the specific number of FISA orders that were allowed to expire during the summer of 2001. One FBI manager stated that no FISA orders targeted against al-Qa段da existed in 2001, others interviewed said there were up to <--> al-Qa段da orders at that time, and an OIPR official explained that approximately two-thirds of the number of FISA orders targeted against al-Qa段da had expired in 2001.
Several organizations played a role in the breakdown of the FISA process in the year before the September 11 attacks. According to FBI personnel, OIPR and the FISA Court erred by requiring much extraneous information in FISA applications, thus increasing the likelihood of mistakes. Bureau agents frequently could not or did not verify the accuracy of information in the FISA applications. The FISA Court痴 order prohibiting an FBI agent from appearing before the Court also apparently had a chilling effect on FBI agents, and they became increasingly unwilling to confirm the veracity of FISA applications.
"