The assertion is 100% correct.

There are other reports out there & some of them do great breakdowns of click volume, click costs, click values & so on ... based on things like: device type (desktop vs tablet vs cell phones, or even across operating systems), branded keywords vs unbranded keywords, text ads vs PLAs/shopping ads, etc.

There are many such reports, but the SEM company which regularly puts out the best report on this front is RKG (which was bought out by Merkle last year http://www.merkleinc.com/news-and-events/press-releases/2014... and even after the buyout is still putting out great reports each quarter).

RKG's most recent report is downloadable here http://www.rimmkaufman.com/digital-marketing-report/ & it is something I read (and recommend) every quarter. :)

In the report, they stated they saw Google dramatically increase minimum CPC on own brand keywords over the past year, that brand keyword cost was up 39% YoY, and that Google was now charging brands more for clicks on their own brand terms than Bing does. You can see a quick review of their report here
http://searchengineland.com/us-paid-search-growing-but-at-sl...

And there might be multiple factors in Google showing fewer ads. Some general assertions and/or hypothesis on potential drivers...

A rise in minimum CPCs on brand keywords might block out some of the lower value 3rd party arbitrage on the branded terms, Google might be showing larger ads (with more ad extensions) above the organic results & fewer ads in the right sidebar, some categories might have PLAs / shopping ads performing so strong that there is less need for text ads, in some categories (like hotel search) Google has effectively turned much of the "organic" search result set into another layer of ads via their hotel price ads, Google includes affiliate links in their knowledge graph, over time more of Google's search volume is on mobile devices with a smaller SERP interface & no right rail to show ads in, over time more of Google's search volume is in emerging markets with less shallower and less mature ad markets, etc etc etc

A few other things worth mentioning on their general economic trends: on smaller devices partners (outside of the big one in Apple) are easier for Google to squeeze out & represent a smaller share of Google's ad revenues, over the last couple years the partner network keeps comprising a smaller percent of Google's overall ad revenue (numerous sources on this front, like http://www.siliconvalleywatcher.com/mt/archives/2013/10/anal... & http://blog.pagefair.com/2014/adsense-smoking-gun/ ), Google is getting higher revenue from clicks on Google.com & their regional search properties but the YouTube pre-roll ads generally go for less money (since they are earlier in the consumer funnel than search is & have less intent than a search does) & drag down the aggregate click price (because Google counts YouTube video ad views as clicks).

One other thing worth mentioning in terms of mobile is that while the mobile click values (and thus CPCs) are lower, Google offsets that by dominating the mobile interface with ads. 3 years back I wrote this post http://www.seobook.com/mobile-seo highlighting how Google had over double the CTR on mobile search ads as they did on desktop search ads. The top graph from that post came from an RKG quarterly report for that quarter.