  We present a simple analytical description of the disruption of star clusters
in a tidal field, which agrees excellently with detailed N-body simulations.
The analytic expression can be used to predict the mass and age histograms of
surviving clusters for any cluster initial mass function and any cluster
formation history. The method is applied to open clusters in the solar
neighbourhood, based on the new cluster sample of Kharchenko et al. From a
comparison between the observed and predicted age distributions in the age
range between 10 Myr to 3 Gyr we find the following results: (1) The disruption
time of a 10^4 M_sun cluster in the solar neighbourhood is about 1.3+/-0.5 Gyr.
This is a factor 5 shorter than derived from N-body simulations of clusters in
the tidal field of the galaxy. (2) The present starformation rate in bound
clusters within 600 pc from the Sun is 5.9+/-0.8 * 10^2 M_sun / Myr, which
corresponds to a surface star formation rate in bound clusters of 5.2+/-0.7
10^(-10) M_sun/yr/pc^2. (3) The age distribution of open clusters shows a bump
between 0.26 and 0.6 Gyr when the cluster formation rate was 2.5 times higher
than before and after. (4) The present star formation rate in bound clusters is
half as small as that derived from the study of embedded clusters. The
difference suggests that half of the clusters in the solar neighbourhood become
unbound within 10 Myr. (5) The most massive clusters within 600 pc had an
initial mass of 3*10^4 M_sun. This is in agreement with the statistically
expected value based on a cluster initial mass function with a slope of -2,
even if the physical upper mass limit is as high as 10^6 M_sun.
