Agreement variation is a critical issue in discussing syntactic configuration and semantic integration. Two competing hypotheses have been proposed to account for how semantic integration contributes to agreement variation: the lexical-grammatical hypothesis and the notional hypothesis. Using data from NOW, a large corpus of World Englishes, this study presents a multifactorial analysis of the probabilistic factors that constrain agreement variation in it-clefts, an important but low-frequency construction, with collective nouns as clefted constituents. We employ random forests and conditional inference trees to examine how the Outer circle varieties have developed preferences different from those of the Inner circle varieties for agreement patterns of it-clefts. The principal findings include: (1) singular agreement is the default pattern worldwide, while plural agreement appears probabilistically along the continuum of collective plurality; (2) Inner circle speakers use more plural agreement than Outer circle speakers, with British English users employing more plural agreement than American English users; and (3) Semantic integration exerts more influence on Inner circle speakers in agreement implementation than on Outer circle speakers, who are more easily affected by morpho-grammatical markers. The quantitative case study on the collective noun team corroborates the lexical-grammatical hypothesis that semantic integration encourages plural agreement. This focused attention on agreement variation in it-clefts with collective nouns as clefted constituents further suggests that the extraposition analysis, rather than the expletive analysis, offers a suitable theoretical model for the syntactic configuration of the it-cleft construction.