16:9 (1.7:1) (16:9 = 4:3) is an aspect ratio with a width of 16 units and height of 9. Since 2010 it has become the most common aspect ratio for televisions and computer monitors, and is also the international standard format of HDTV, Full HD, non-HD digital television and analog widescreen television. This has replaced the old . 

Dr. Kerns H. Powers, a member of the SMPTE Working Group on High-Definition Electronic Production, first proposed the 16:9 (1.7:1) aspect ratio at a time when nobody was creating 16:9 videos. The popular choices in 1980 were: 1.3:1 (based on television standard's ratio at the time), 1.6:1 (the European "flat" ratio), 1.85:1 (the American "flat" ratio), 2.20:1 (the ratio of 70 mm films and Panavision) and 2.39:1 (the CinemaScope ratio for anamorphic widescreen films). 

Powers cut out rectangles with equal areas, shaped to match each of the popular aspect ratios. When overlapped with their center points aligned, he found that all of those aspect ratio rectangles fit within an outer rectangle with an aspect ratio of 1.7:1 and all of them also covered a smaller common inner rectangle with the same aspect ratio 1.7:1. The value found by Powers is exactly the geometric mean of the extreme aspect ratios, 4:3 (1.3:1) and 2.35:1 (or 64:27, see also for more information), √ ≈ 1.770 which is coincidentally close to 16:9 (1.7:1). Applying the same geometric mean technique to 16:9 and 4:3 yields the aspect ratio, which is likewise used as a compromise between these ratios.
What is the most common aspect ratio for TVs?
Is this the international standard?
For which types of TV?
And?
Anything else?
Who proposed this ratio?
Is he a doctor?
Was he a member of any professional organizations at the time?
Which one?
What decade did he make this proposal?
Were there other choices then?
Was that considered standard?
What about in Europe?
Was that considered flat?
Did America have a flat ratio?
What was it?
What was used for 70mm movies?
Was that used for anything else?
What?
Did Powers use rectangles with different areas?
16:9 = 4:3) is an aspect ratio with a width of 16 units and height of 9. Since 2010 it has become the most common aspect ratio for televisions and computer monitors
16:9 = 4:3) is an aspect ratio with a width of 16 units and height of 9. Since 2010 it has become the most common aspect ratio for televisions and computer monitors
yes
 is also the international standard format of HDTV
HDTV
nternational standard format of HDTV,
Full HD
Full HD
non-HD digital television and analog widescreen television
 non-HD digital television and analog widescreen television
Kerns H. Powers
Kerns H. Powers, a member of the SMPTE Working Group on High-Definition Electronic Production, first proposed the 16:9
yes
Dr. Kerns H. Powers, 
yes
a member of the SMPTE Working Group on High-Definition Electronic Production,
SMPTE Working Group on High-Definition Electronic Production
SMPTE Working Group on High-Definition Electronic Production
1980s
he popular choices in 1980 
1.3:1
The popular choices in 1980 were: 1.3:1
yes
(based on television standard's ratio at the time
1.6:1
1.6:1
yes
(the European "flat" ratio
yes
1.85:1 (the American "flat" ratio
1.85:1
1.85:1
2.20:1
), 2.20:1 
yes
and Panavision
Panavision
Panavision
no
cut out rectangles with equal areas