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Tech jobs are now white collar trades that need apprentices
(www.theregister.com)
This is a most excellent place for technology news and articles.
Certifications are there to assure the employer that A) you know something B) you are able to be trained. The reason you use 20-30% is because few jobs on the planet require you to know everything. The certification assures that you are at least well read on whatever 20-30% is thrown your way.