-j<N>, -j <N> and --jobs <N> not recognized

All three different ways of specifying concurrency level

    cd /usr/src/linux-x.x.x
    export CONCURRENCY_LEVEL=16
    make-kpkg --initrd --jobs 16 buildpackage
    make-kpkg --initrd -j 16 buildpackage
    make-kpkg --initrd -j16 buildpackage # not in man page, but common for GNU make

don't show any parallelization which comes close to 5 % of the usual effect such a value for the `CONCURRENCY_LEVEL` has, i.e. I've experienced with all projects I've compiled so far with `-j16` option specified that all CPU cores are used 100 % during > 90 % of the time of the build, i.e. rarly more than 50 % usage of 1 or 2 cores. With `make-kpkg` I see for 5 minutes the same effect like when I omit the `-j` option. I make the 100 % usage experience with

    -Computer-
    Processor : 8x Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz
    Memory : 16291MB (1409MB used)
    Operating System : Ubuntu 14.04.1 LTS
    -SCSI Disks-
    ATA ST1000LM014-1EJ1

experienced with make-kpkg 12.036+nmu3 on Ubuntu 14.04.1.