The distribution of bar strengths in disk galaxies is of fundamental importance in studies of galaxy evolution for two reasons. First, bars are the most important morphological features of galaxies that cross the spiral-S0 divide. They are a potentially fruitful way of comparing these two classes of disk galaxies and perhaps for better understanding the relation between them. Secondly, recent theoretical studies by Athanassoula show how a live halo can strongly impact the bar strength, while studies by Bournaud and Combes have shown that gas accretion can cause bar strength to be periodically variable over a Hubble time. The distribution of bar strengths should be a complex combination of halo-bar-disk angular momentum exchanges, external gas accretions, and possible effects of interactions, all over a Hubble time. The recent development of the gravitational torque method for quantifying bar strength, in conjunction with the availability of statistically well-defined image databases such as the Ohio State survey, has led to the first measures of the distribution of bar strengths in normal disk galaxies. After removal of the effects of spiral arm torques, the distribution of maximum relative bar torques in normal, massive spiral galaxies shows an approximately exponential decline with increasing bar strength. There are three issues that will be addressed in this presentation: (1) How do uncertainties in the assumed vertical scale heights, orientation parameters, and the dark matter affect this distribution? (2) Which of the above physical effects might have the greatest impact on the observed distribution? and (3) How do early-type galaxy bars compare with those seen in spirals, based on Fourier dissection studies and the same kind of bar strength analysis? This work has been supported by NSF grants AST020-5143 and AST050-7140, the Academy of Finland, the Magnus Ehrnrooth Foundation, the Leverhulme Trust, and the Anglo-American Chairman's Fund.