  We report on the normal-superconducting phase transition in thick
$\mathrm{YBa_{2}Cu_{3}O_{7-\delta}}$ films in zero magnetic field. We find
significant finite-size effects at low currents even in our thickest films ($d
= 3200$ \AA). Using data at higher currents, we can unambiguously find $T_c$
and $z$, and show $z = 2.1 \pm 0.15$, as expected for the three-dimensional XY
model with diffusive dynamics. The crossover to two-dimensional behavior, seen
by other researchers in thinner films ($d \leq 500$ \AA), obscures the
three-dimensional transition in both zero field and the vortex-glass transition
in field, leading to incorrect values of $T_c$ (or $T_g$), $\nu$, and $z$. The
finite-size effects, usually ignored in thick films, are an explanation for the
wide range of critical exponents found in the literature.
