  Jung's theorem says that planar sets of diameter $1$ can be covered by a
closed circular disc of radius $\frac 1{\sqrt3}$. In this paper we will
restrict ourselves to finite point sets and consider a fractional Jung-type
problem. Let $\mathcal{P}_n$ be the family of all finite sets of $n$ points of
diameter $1$. Let the function value $N_n(r)$ ($0 < r \leq 1$) be the largest
integer $k$ so that for every point set $P \in \mathcal{P}_n$ there is a circle
of radius $r$ which covers at least $k$ points of $P$. We give many lower and
upper bounds for $N_n(r)$ and determine intervals of $(0,1]$ where exact values
of $N_n(r)$ can be determined. Among others we show the $n\leq
N_{3n}(\frac{1}{2}) \leq n+1$ and $N_n(\frac{1}{4}) = \lceil \frac{n}{7}
\rceil$ for all $n\neq 7$.
