  We study the fluence distributions of over 3040 bursts from SGR 1806-20 and
over 1963 bursts from SGR 1900+14 using the complete set of observations
available from the Rossi X-Ray Timing Explorer/Proportional Counter Array
through March 2011. Cumulative event distributions are presented for both
sources and are fitted with single and broken power laws as well as an
exponential cutoff. The distributions are best fit by a broken power law with
exponential cutoff, however the statistical significance of the cutoff is not
high and the upper portion of the broken power law can be explained as the
expected number of false bursts due to random noise fluctuations. Event
distributions are also examined in high and low burst rate regimes and power
law indices are found to be consistent, independent of the burst rate. The
contribution function of the event fluence is calculated. This distribution
shows that the energy released in the SGR bursts is dominated by the most
powerful events for both sources. The power law nature of these distributions
combined with the dominant energy dissipation of the system occurring in the
large, less frequent bursts is indicative of a self-organized critical system
(SOC), as suggested by Go\u{g}us, et al. in 1999.
