  We analyze three years (1998-2000) of OGLE observations of microlensing
events to place limits on the abundance of planets with a planet-to-star mass
ratio $q=10^{-3}$ at distances $\sim 1-4$AU from their host stars, i.e. `cool
Jupiters'. We fit a total of 145 events using a maximum likelihood fit that
adjusts 6 parameters. Each data point on the lightcurve allows us to exclude
planets close to the two images of the source appearing on opposite sides of
the Einstein ring of the lens star. We proceed to compute detection probability
maps for each event, using $\Delta\chi^2$ threshold values of 25, 60, 100 and
combine the results from all events to place global constraints. Our selection
criteria returned 5 candidate events for a planet with mass ratio $q=10^{-3}$.
Only two of these remained as plausible candidates after three were rejected
due to poor data quality at the time of the anomalies. Our results suggest that
less than 21 ($n$)% of the lens stars have Jupiter-mass planets orbiting them
at an orbital radius of $1 < a < 4$ AU. $n \le 2$ is the number of planet
anomaly candidates that are actually due to planets. The datasets presented
here were obtained from the DoPhot analysis of the events available at the OGLE
website. The main conclusion of this work is that observing time is more
efficiently allocated by observing many events with sampling intervals that
produce non-overlapping detection zones than using intensive sampling on a
small number of events.

Astrophysics