[excerpt]
IMMIGRATION AND NATIONALITY ACT[…..]
Sec. 201.
[….]
(d) Worldwide level of employment-based immigrants
(1) The worldwide level of employment-based immigrants under this subsection for a fiscal year is equal to-
(A) 140,000 plus
(B) the number computed under paragraph (2).
(2)(A) The number computer under this paragraph for fiscal year 1992 is zero.
(B) The number computed under this paragraph for fiscal year 1993 is the difference (if any) between the worldwide level established under paragraph (1) for the previous fiscal year and the number of visas issued under section 203(b) during that fiscal year.
(C) The number computed under this paragraph for a subsequent fiscal year is the difference (if any) between the maximum number of visas which may be issued under section 203(a) (relating to family-sponsored immigrants) during the previous fiscal year and the number of visas issued under that section during that year.
[….]