syntactic complexity can be measured in terms of the number of immediate constituents of a syntactic construction.
This property has been shown to depend on the frequency of a construction type and vice versa. In the framework of synergetic linguistics, it is also connected with position (within a mother constituent) and length (measured in terms of the number of terminal nodes.
This dependency models a hypothesis which is a modified version of Hawkins' Early Immediate Constituent principle.
Hawkins, John (1994): A performance theory of order and constituency. Cambridge: Cambridge University Press.
Köhler, Reinhard (1986): Zur linguistischen Synergetik. Struktur und Dynamik der Lexik. Bochum: Brockmeyer.
Köhler, Reinhard (1999): Syntactic structures: properties and interrelations. In Journal of Quantitative Linguistics 6, 46-57.
Köhler, Reinhard/Altmann, Gabriel (2000): Probability distributions of syntactic units and properties. In: Journal of Quantitative Linguistics 7, 189-200.