Below is the list of the languages sorted by the number of L2 speakers (more than one million of them).
L2 speakers appear in two occasions: * First and important to us is about languages used for wider communication. For example, French is L2 among educated people of West Africa. * The second type is related to the native languages in not so good position (either dying or reviving). For example, English is L1 language of the most of Native Americans, as well as Russian is L1 language of the most of ethnicities of former Soviet Union, while their own languages are L2 ones. (They are important in other cases, but not for this purpose.)
I omitted English (there is no sense, as we are communicating in English and English is default for all the localization) and few spoken languages (our content is [mostly] written).
I also removed some languages which belong to the second category (Irish Gaelic and Scots, for example), but it could be the case that some of the languages from the list belong to that category, as well (though I am pretty sure they don't).
There are languages inside of this list with well developed Wikimedia projects and without particular need to promote work on Wikimedia projects among them: French, Spanish and German are the examples. There is no Russian inside of the list, as it's usually L1 language, as mentioned above, but it belongs to the category of the languages with well developed Wikimedia projects.
There are also languages spoken in countries with low level of internet access and issues much more important than writing an encyclopedia, like Congo Swahili is. Those are the areas not yet ready even for the projects like OLPC is and we don't have a lot to do there.
But there are a number of languages in between with active chapter(s) or user group(s) inside of relevant countries. Those languages should be the priority in promotion collaboration.
They are: Arabic (Arabic user groups), Indonesian (WM ID), Hindi (WM IN), Urdu (Pakistani user group), Thai (Thailand UG), Bengali (WM BD), Zulu (WM ZA), Hausa (West African user groups), Xhosa (WM ZA), Afrikaans (WM ZA), Kannada (WM IN), Telugu (WM IN), Tsonga (WM ZA), Malay (WM ID and Malaysian Wikimedians), Marathi (WM IN).
The priorities for those languages should include (but likely not limited to): * Translation of MediaWiki messages should be 100%. * Those languages should be priorities for every document which should be translated. For example, ongoing Board elections; but also various Meta pages. * We should have the pool of literate people in those languages for various purposes, not just for translation. For example, if we want to create projects in languages of Pakistan, we should have a number of literate Urdu speakers, willing to help newcomers speaking Urdu as their L2 language.
Will be back with other languages-related data :)
LanguageCodeL1 speakersL2 speakersStandard Arabicarb206,000,000246,000,000Mandarin Chinesecmn847,808,270178,000,000Indonesianind23,200,480140,000,000Hindihin 260,333,620120,000,000Spanishspa398,931,84096,990,000Urduurd64,035,800 94,000,000Frenchfra75,916,15087,000,000Thaitha20,396,93040,000,000Bengaliben 189,261,20019,200,000Zuluzul11,969,10015,700,000Hausahau25,109,00015,000,000 Xhosaxho8,177,30011,000,000Afrikaansafr7,096,81010,300,000Bamanankanbam 4,072,04010,000,000Burmesemya32,035,30010,000,000Congo Swahiliswc1,000 9,100,000Northern Sothonso4,631,0009,100,000Kannadakan37,739,0409,000,000 Germandeu78,093,9808,000,000Tamiltam68,776,4608,000,000Juladyu2,550,000 7,000,000Lingalalin2,141,3007,000,000Koongokng5,016,5005,000,000Telugutel 74,049,0005,000,000Ibibioibb1,500,0004,500,000Tok Pisintpi122,0004,000,000 Kriokri495,6004,000,000Amharicamh21,811,6004,000,000Bangalabxg~0 3,500,000Tsongatso4,009,0003,400,000Malayzlm15,848,5003,000,000Marathimar 71,780,6603,000,000Sinhalasin15,613,9802,000,000Efikefi405,2602,000,000Duala dua87,7002,000,000Yorubayor19,380,8002,000,000Shonasna10,741,7001,800,000 Vendaven1,294,0001,700,000Sangosag404,0001,600,000Manado Malayxmm850,000 1,500,000Sylhetisyl10,300,0001,500,000Ambonese Malayabs245,0201,400,000 Ndebelenbl1,090,0001,400,000Rakhinerki1,000,0001,020,000Gandalug4,130,000 1,000,000Akanaka8,314,6001,000,000Khmerkhm14,224,5001,000,000