State Education Department and based on differences in labor market costs, and the Geographic Cost of Education Index (GCEI), provided by the National Center for Education Statistics. The latter index was developed by Jay Chambers, one of the principal authors of the New York Adequacy Study, a cost analysis project cosponsored by plaintiff CFE in 2003-2004. The GCEI attempts to measure the attractiveness of employment within a particular district, one of the key determinants of the cost of providing education. S & P used what was then the most recent, publicly available version of the GCEI, a 1997 update by Chambers. Finally, amounts were adjusted for inflation to reflect January 2004 purchasing power. [*5] S & P thus calculated "sound basic education" spending estimates for each school district, using the two regional cost indices and the four alternative criteria for identifying successful school districts. The spending estimates did not include capital, debt or transportation costs. Finally, these figures were compared with amounts actually spent in 2002-2003, in order to identify "spending gaps." Applying the GCEI, the estimated spending gaps for New York City ranged from $1.93 billion to $2.53 billion and the statewide spending gaps from $2.45 billion to $3.39 billion, depending on which criterion for successful school districts was used. (New York City's spending gap thus comprised 74% to 79% of the State's total gap.) When the NY RCI was applied, the estimated spending gaps were larger, ranging from $4.05 billion to $4.69 billion for New York City, and $4.61 billion to{**8 NY3d at 24} $5.57 billion statewide.[FN3] Applying the GCEI and the Board of Regents approach to identifying successful schools, the spending gap for New York City, in 2004 dollars, was $1.93 billion. Governor Pataki convened the Legislature in extraordinary session on July 20, 2004, and proposed a program bill to the Senate, incorporating the Zarb Commission's methodology. The Senate passed an amended version of the bill. Ultimately, the legislation was not enacted. In both versions of the bill, the Legislature would have found that the actual costs of providing a sound basic education should be determined using the Board of Regents approach to identifying successful schools (which had picked out 281 of 699 school districts), the S & P weightings for students with special needs, the GCEI, and the cost-effectiveness filter (see 2004 Extraordinary Session NY Senate Bill S 1-A, § 1, at 2 [July 20, 2004]; 2004 NY Senate Bill S 7684-B, § 2, at 2 [July 20, 2004]). In other words, Governor Pataki and the Senate endorsed the approach that generated a minimum figure of $1.93 billion as the estimated spending gap in operating expenses for New York City. In his State Education Reform Plan, submitted in the course of this litigation, the Governor concluded that "the S&P analysis as adopted by the Zarb Commission and by State defendants determined that $2.5 billion in additional revenues statewide (equating to $1.9 billion in New York City) was a valid determination of the cost of providing a sound basic education in New York City" (State Education Reform Plan, at 14 [Aug. 12, 2004]).