Google Trends shows what we already know: subscription services are increasingly popular while interest in paid downloads has peaked. But Google Trends, a Google service that graphs the frequency of search terms, also shows the popularity of music services in relation to one another.

A blog post by the Echo Nest's Paul Lamere showed the various trends of various digital music services at Google Trends. Lamere performed one query at a time. While the results were insightful, I expanded the searches by combining search terms and examining how services are trending in various countries. Examining trends by country is especially revealing because adoption of legal music services takes place at difference paces and on different timelines from country to country.

It’s easy to understand why Apple is launching an Internet radio service. SoundScan and IFPI data have already showed that download’s share of digital music peaked in the US and globally in 2011. Google Trends also shows interest in downloads is waning.

U.S. web searches for iTunes and Pandora since 2004.

Google Trends shows US web searches for iTunes peaked in 2011 and are currently at levels last seen in early 2009. Globally, iTunes web searches were roughly equal in December 2010 and December 2011 but have fallen ever since. Searches for iTunes have also subsided in the major music markets such as the UK, Germany, France and Japan.

As a search term, iTunes encompasses music downloads as well as video, apps and books. The term shows the general interest in iTunes software and its stores. The term "iTunes music" shows a similar trend: it peaked in December 2011 and has since fallen to 2010 levels.

The decline in iTunes searches is even more obvious in smaller markets that were early to adopt streaming services. In Norway, iTunes searches peaked in December 2009 and fell 55% by December 2012. In Sweden, iTunes searches (pictured below) peaked in October 2009, fell 22% by December and dropped another 38% by August, the lowest mark since June 2009. Spotify launched in both countries in late 2008.

Web searches for iTunes in Sweden peaked in October 2011 and are currently at levels last seen in early 2009.

Google Trends also shows relative popularity. A query of web search traffic for four US streaming services shows now only how each service trends but also how interest in the services compares to one another.

Spotify and Grooveshark are headed in opposite directions. Spotify peaked in July 2011 -- the month of its US launch -- and has risen steadily after a sharp post-launch decline. Grooveshark peaked in February 2011 and has declined sharply since then.

Rdio currently gets about one-fifteenth the searches of Spotify (6 versus 76 on scale of 100) but has risen steadily over the years. Interest appears to have grown this year as Rdio searches in the US doubled from February to August.

Even though iTunes searches are declining while some streaming services are seeing gains, it’s important to keep their relative popularity in perspective. In August, iTunes got about 3.9 times more US web searches than Spotify and 54 times more searches than Rdio.

Web searches in the United States for Grooveshark (blue), Rdio (red), Spotify (gold) and Rhapsody (green) from 2004 to present.

The graph above shows web searches in the United States for Grooveshark, Rdio, Spotify and Rhapsody from 2004 to present. Note that searches for Rhapsody cover the music service as well as phrases that include the word rhapsody. The song "Bohemian Rhapsody" is the most-searched term that includes the word Rhapsody. The search term "Rhapsody music" is searched 20% as often as "Bohemian Rhapsody."

Global web searches for Deezer (red) and Spotify (blue) from 2004 to present.

Deezer and Spotify, the two leading subscription services, are headed in the opposite directions. Deezer searches peaked in December 2008, coincidentally the same month Spotify launched, but has fallen fairly consistently ever since. Deezer was a much different service back then: it didn't have a licensing deal with all four majors until April 2009 and didn't require registration until February 2009. In contrast, searches for Spotify have steadily increased since its October 2008 launch, matching Deezer search traffic in January and now surpassing it by 38%.

Google Trends is great for getting a general idea of product trends but has limitations. The trend of Deezer searches is an example. Deezer is a much different service than it was in 2009. Originally launched in 2007 as a free streaming service called Blogmusik, Deezer originally limited free streaming and expanded its free, ad-supported tier in December. Thus, a decline in Deezer searches does not necessarily reflect a waning interest in the current Deezer product.