Building Design has released their annual ranking, The WA100, of the world’s largest architecture firms. Coming in the #1 spot (up from #2 last year) is Nikken Sekkei (ranked #4) were the top 3 earners of 2012, each making over $400 million US Dollars in Fee Income.

Of the top 10 largest firms, 5 are based in North America, 3 in Asia, and 1 in the UK (Aedas, which ranked 5th, is dually based in both China and the UK). A similar trend is also evident in the list as a whole - as you can see from the graphic we compiled (after the break), US firms remain the biggest employers of architects and the highest-earners. Although the UK represents about half the number of employed architects as the US, UK firms earned almost as much in fee income.

Interestingly, the only firms to grace both the Top 10 list and Building Design's survey of the Top 5 Most Admired Firms of 2012, were Gensler (#2 Largest; #4 Most Admired) and Foster & Partners (#10 Largest; #1 Most Admired). Rogers Stirk Harbour & Partners, ranked as the 45th largest firm).

See our graphic and the full list of the world’s largest firms, after the break...

The Full List of the World’s 100 Largest Firms, Ranked by Size

1. Aecom (USA. 1,370 architects employed. Over $400m Fee Income)

2. Gensler (USA. 1,346. Over $400m)

3. IBI Group (Canada. 1,129. $160-169m)

4. Nikken Sekkei (Japan. 1,109. Over $400m)

5. Aedas (China/UK. 1, 078. $200-209m)

6. Perkins & Will (USA. 771. $220-229m)

7. DP Architects (Singapore. 736. $70-79m)

8. HOK (USA. 715. $240-249m)

9. Samoo Architects & Engineers (South Korea. 712. $250-259m)

10. Foster & Partners (UK. 646. $200-209m)

11. Stantec (Canada. 643. $210-219m)

12. HDR Architecture (USA. 640. $280-289m)

12. RSP Architects (Singapore. 640. - )

14. P & T Architects (Hong Kong. 624. $130-139m)

15. Sweco (Sweden. 600. $70-79m)

16. Atkins (UK. 597. $100-109m)

17. Woods Bagot (Australia. 565. $130-139m)

18. Jacobs (UK/USA. 547. $200-209m)

19. Skidmore Owings & Merrill (USA. 543. $200-209m)

20. Cannon Design (USA. 539. $130-139m)

21. Heerim Architects & Planners (South Korea. 470. $170-179m)

22. Perkins Eastman (USA. 455. $140-149m)

23. GMP (Germany. 445. $70-79m)

24. Leo A Daly (USA. 436. $130-139m)

25. Nihon Sekkei (Japan. 426. $170-179m)

26. Kunwon Architects & Engineers (South Korea. 421. $50-59m)

26. SmithGroup JJR (USA. 421. $110-119m)

28. Tengbom (Sweden. 420. $70-79m)

29. Kohn Pedersen Fox Associates (USA. 405. $110-119m)

29. NBBJ (USA. 405. $170-179m)

31. Hassell (Australia. 395. $120-129m)

32. BDP (UK. 382. $100-109m)

33. Kume Sekkei (Japan. 376. $120-129m)

34. ATP Architects & Engineers (Austria. 320. $70-79m)

34. Mitsubishi Jisho Sekkei (Japan. 320. $210-219m)

36. White Arkitekter (Sweden. 306. $80-89m)

37. DLR Group (USA. 300. $120-129m)

37. HKS (USA. 300. $150-159m)

39. Cox Architecture (Australia. 289. $60-69m)

40. Leigh & Orange (Hong Kong. 288. $40-49m)

41. Henn Architekten (Germany. 280. $60-69m)

42. HBO+EMTB (Australia. 279. $80-89m)

43. RTKL Associates (USA. 269. $200-209m)

44. KEO International (Kuwait. 256. $110-119m)

45. Zaha Hadid Architects (UK. 246. - )

46. ZGF Architects (USA. 245. $60-69m)

47. Arup Associates and Arup (UK. 226. $40-49m)

48. Benoy (UK. 223. $60-69m)

49. Dewan Architects & Engineers (UAE. 220. $60-69m)

50. ACXT-IDOM (Spain. 215. $40-49m)

51. DWP (Thailand. 205. $40-49m)

52. Architect Hafeez Contractor (India. 200. $30-39m)

52. Valode & Pistre (France. 200. $40-49m)

52. Wong Tung & Partners (Hong Kong. 200. $50-59m)

55. Archial NORR (UK. 198. $70-79m)

56. Chapman Taylor (UK. 196. $40-49m)

57. Gansam Architects & Partners (South Korea. 191. $50-59m)

58. B+H Architects (Canada. 190. $50-59m)

59. Ishimoto Architectural & Engineering (Japan. 188. $60-69m)

60. LINK Arkitektur (Norway. 177. $40-49m)

61. Capita Symonds (UK. 170. $30-39m)

62. Ronald Lu & Partners (Hong Kong. 169. $30-39m)

63. Broadway Malyan (UK. 165. $50-59m)

64. CF Møller Architects (Denmark. 164. $40-49m)

65. Allies & Morrison (UK. 160. $20-29m)

65. Devereux Architects (UK. 160. $10-19m)

65. GHD (Australia. 160. $140-149m)

65. GVA & Asociados (Mexico. 160. $20-29m)

69. Archetype Group (Vietnam. 158. $10-19m)

69. AXS Satow (Japan. 158. $60-69m)

71. Henning Larsen Architects (Denmark. 155. $20-29m)

72. Langdon Wilson International (USA. 153. $40-49m)

73. AS Architecture-Studio (France. 150. $20-29m)

73. Jaspers-Eyers Architects (Belgium. 150. $20-29m)

73. Wilson Associates (USA. 150. $50-59m)

76. Wilmotte & Associés (France. 149. $30-39m)

77. Showa Sekkei (Japan. 141. Under $5m)

78. Ramboll Architecture & Planning (Norway. 140. $30-39m)

79. Sheppard Robson (UK. 139. $20-29m)

80. Aidea (Philippines. 131. $5-9m)

81. CP Kukreja (India. 130. $5-9m)

82. Rober A.M. Stern Architects (USA. 126. $50-59m)

83. PageSoutherlandPage (USA. 125. $90-99m)

83. Sinclair Knight Merz (125. $30-39m)

85. Progetto CMR (Italy. 124. $10-19m)

86. PBK (USA. 121. $40-49m)

86. Populous (UK. 121. -)

88. Space Matrix (Singapore. 120. $10-19m)

88. TP Bennett (UK. 120. $30-39m)

90. PRP Architects (UK. 119. $20-29m)

91. Aukett FItzroy Robinson (UK. 114. $10-19m)

92. Palafox Associates (Philippines. 112. $5-9m)

93. Hames Sharley (Australia. 110. $20-29m)

93. Morphogenesis (India. 110. $5-9m)

95. AIA Architectes Ingénierus Associés (France. 104. $20-29m)

96. Thomson Adsett Architects (Australia. 103. $20-29m)

97. 3DReid (UK. 100. $20-29m)

97. UN Studio (100. $10-19m)

99. 10 Design (UK/Hong Kong. 96. $20-29m)

99. Diamond Schmitt Architects (Canada. 96. $20-29m)