  Spacetime supersymmetry is widely believed to play an important role in most
fundamental theories of physics, and is usually invoked in order to address
problems of naturalness. In this paper, we examine the question of whether
supersymmetry itself is ``natural'' (i.e., likely to exist as a fundamental
component of nature at high energy scales). Our approach to answering this
question is based on a statistical examination of the heterotic string
landscape, and our conclusion is that supersymmetry is an exceedingly rare
phenomenon. We also find that the likelihood of supersymmetry appearing at the
string scale is dependent on the gauge symmetries present at the string scale,
with certain gauge groups strongly favoring the appearance of N=1 supersymmetry
and others not. This article summarizes several recent papers, yet also
contains some new results. In particular, one new result is that the heterotic
landscape appears to favor either the non-supersymmetric Standard Model or an
N=1 SUSY GUT gauge group at the string scale; by contrast, the opposite
outcomes (namely the MSSM or a non-supersymmetric GUT) are significantly
disfavored.
