bash-4.2$ jobscount() {
>   local stopped=$(jobs -sp | wc -l)
>   local running=$(jobs -rp | wc -l)
>   ((running+stopped)) && echo -n "${running}r/${stopped}s "
> }

bash-4.2$ PS1=' \w $(jobscount)\$ '

 ~ $ jobs

 ~ $ sleep 100 &
[1] 2325

 ~ 1r/0s $ sleep 110 &
[2] 2333

 ~ 2r/0s $ jobs
[1]-  Running                 sleep 100 &
[2]+  Running                 sleep 110 &

 ~ 2r/0s $ sleep 120
^Z
[3]+  Stopped                 sleep 120

 ~ 2r/1s $ jobs
[1]   Running                 sleep 100 &
[2]-  Running                 sleep 110 &
[3]+  Stopped                 sleep 120

 ~ 2r/1s $ bash --version
GNU bash, version 4.2.42(1)-release (i686-frugalware-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.