  We test the existence of a neighborhood based peer effect around
participation in an incentive based conservation program called `Water Smart
Landscapes' (WSL) in the city of Las Vegas, Nevada. We use 15 years of
geo-coded daily records of WSL program applications and approvals compiled by
the Southern Nevada Water Authority and Clark County Tax Assessors rolls for
home characteristics. We use this data to test whether a spatially mediated
peer effect can be observed in WSL participation likelihood at the household
level. We show that epidemic spreading models provide more flexibility in
modeling assumptions, and also provide one mechanism for addressing problems
associated with correlated unobservables than hazards models which can also be
applied to address the same questions. We build networks of neighborhood based
peers for 16 randomly selected neighborhoods in Las Vegas and test for the
existence of a peer based influence on WSL participation by using a
Susceptible-Exposed-Infected-Recovered epidemic spreading model (SEIR), in
which a home can become infected via autoinfection or through contagion from
its infected neighbors. We show that this type of epidemic model can be
directly recast to an additive-multiplicative hazard model, but not to purely
multiplicative one. Using both inference and prediction approaches we find
evidence of peer effects in several Las Vegas neighborhoods.
