Interest in software consulting has not gone down 80% overall, it has gone down 80% relative to total search volume over time.<p>Here's the same graph with "linux" and "news" added:
<a href="http://www.google.com/trends/explore#q=software%20consulting%2C%20software%20consultant%2C%20linux%2C%20news&cmpt=q" rel="nofollow">http://www.google.com/trends/explore#q=software%20consulting...</a><p>Linux has gone down over time, while a generic term like "news" has gone up. I find it implausible that interest in Linux has decreased, but rather the internet is being adopted by more of the general population.
These graphs make it hard to separate software consulting, the particular shape of a contractual business arrangement, vs "software consulting" used as a buzzword phrase to describe something else, e.g. outsourcing (I see large numbers of hits in India) - and buzzwords change over time, like fashions.
No real change when you limit to US searches since 2007:
<a href="http://www.google.com/trends/explore#q=software%20consultant&geo=US&date=1%2F2007%2012m&cmpt=q" rel="nofollow">http://www.google.com/trends/explore#q=software%20consultant...</a>
Interest in "computers" also down by 80% since 2004 in Google Trends: <a href="http://www.google.com/trends/explore#q=computers&cmpt=q" rel="nofollow">http://www.google.com/trends/explore#q=computers&cmpt=q</a>