To my surprise and according to DENIC, .DE was still the most popular (serious*) country code top-level domain (ccTLD) by December 2014:
Right, .DE ranks only #3 in that graph. However, the popular .COM is not a country code top-level domain — although widespread in the U.S., it has no geographical implications. Furthermore, while .TK technically is a country code domain, it is very different from regular ones as discussed by the end of this article.
Surprisingly, .CN (China’s ccTLD) still did not overtake Germany’s .DE: In a 2013 report, CENTR (the European country code TLD organisation) revealed an especially large growth for .CN within six months only:
Keeping that pace, it would not take long until .CN overtakes .DE, too. But does the popularity of .CN constantly grow that fast? No. According to this report, it grew by only 1.8 % between May and August 2014. From these data it can be concluded that .CN’s growth rate underlies strong fluctuations. It is still significantly larger than DE’s growth rate, but according to DENIC the absolute difference between .DE and .CN domain registrations was still about 4.5 million by the end of 2014. That is, .CN probably will overtake .DE, but it will rather happen within the next couple of years than tomorrow.
Liechtenstein: even more domains than letter boxes?
An interesting fact: normalized by population, Liechtenstein holds a record: it has 1.76 ccTLD’s registered per citizen, compared to 0.19 in case of Germany (CENTR report from September 2014).
Why .TK is not comparable to .DE, .UK, and .CN (*)
From the figures you inferred that .TK is the largest country-related zone with about 26 million reported domain names as of 2014. Quite a phenomenon you should know about! This domain is based on a fundamentally different business model than traditional domains such as .DE. I have two quotes for you, describing the situation:
.tk is the country-code domain of Tokelau, a small group of islands and a territory of New Zealand. Domains under .tk are offered free of charge for an initial period. Once expired, they are used for advertising purposes by the registry operator. […] No clear geographical relationship exists between .tk domains and the territory of Tokelau.
Tokelau […] is a territory of New Zealand in the South Pacific Ocean consisting of three atolls with a combined land area of 10 km^2. The owner of all free .tk domains is the registry. If you want to own the domain, you must pay. Pricing is from $6.95 per year with a minimum two-year registration period; although domains containing one, two or three characters or those with branded, generic or common words are considered premium and are priced higher. As a result, one sixth of the Tokelau economy consists of income from .tk domain names.
Long-term development towards steady-state
In another extensive report from 2013, CENTR states that the growth rate of country code top-level domain names has halved between 2008 and 2013. That is, the Internet is slowly progressing towards saturation and steady-state with respect to domain names:
The average increase in the latter half of 2013 of 264,000 domains per month is half the average increase of 528,000 evidenced in the first part of 2008.
Interesting: most of the data used in CENTR reports seems to stem from a single source — a commercial “provider of data and analysis for the domain name industry”: zooknic.com
Are you aware of additional interesting insights derived from the development of top-level domain popularity?