Speed up build phase with "make -j"

[js]

http://www.macosxhints.com/article.php?story=20070524074057479
>From this article, I learned how we can easily speed up build phase of MacPorts.

$ sudo port clean lv
--->  Cleaning lv
$ sudo port configure lv
--->  Fetching lv
--->  Verifying checksum(s) for lv
--->  Extracting lv
--->  Applying patches to lv
--->  Configuring lv
$ time sudo port build lv
--->  Building lv

real    0m6.177s
user    0m4.666s
sys     0m1.035s

$ sudo port clean lv
--->  Cleaning lv
$ sudo port configure lv
--->  Fetching lv
--->  Verifying checksum(s) for lv
--->  Extracting lv
--->  Applying patches to lv
--->  Configuring lv
$ time sudo port build lv build.args="-j"
--->  Building lv

real    0m3.454s
user    0m4.696s
sys     0m1.091s

Can I make this behavior (-j) default for all ports using make?

Thank you.