Thickness-dependent bulk properties and weak antilocalization effect in topological insulator Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math>Se<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>3</mml:mn></mml:msub></mml:math>

We show that a number of transport properties in topological insulator (TI) Bi${}_{2}$Se${}_{3}$ exhibit striking thickness dependences over a range of up to five orders of thickness (3 nm--170 \ensuremath{\mu}m). Volume carrier density decreased with thickness, presumably due to diffusion-limited formation of selenium vacancies. Mobility increased linearly with thickness in the thin film regime and saturated in the thick limit. The weak antilocalization effect was dominated by a single two-dimensional channel over two decades of thickness. The sublinear thickness-dependence of the phase coherence length suggests the presence of strong coupling between the surface and bulk states.