  The most common way to simplify extensive Monte-Carlo simulations of air
showers is to use the thinning approximation. We study its effect on the
physical parameters reconstructed from simulated showers. To this end, we have
created a library of showers simulated without thinning with energies from
10^17 eV to 10^18 eV, various zenith angles and primaries. This library is
publicly available. Physically interesting applications of the showers
simulated without thinning are discussed. Observables reconstructed from these
showers are compared to those obtained with the thinning approximation. The
amount of artificial fluctuations introduced by thinning is estimated. A simple
method, multisampling, is suggested which results in a controllable suppression
of artificial fluctuations and at the same time requires less demanding
computational resources as compared to the usual thinning.
