Number of firms in the US  Auto Industry
1900 1910 1920 1930 1940 1950 1960
75
65
55
45
35
25
15
  5
Entry began slowly but advanced rapidly after 1900.
From 1894 to 1918 60 firms entered,. Peaked at 75 firms in 1923. In the next two years nearly 1/3rd of the industry 23 firms left.
Depression saw another 20 go
1923 Dodge introduced the all steel closed-body automobile
By 1925 half of all US production was all steel closed body.
By 1926 80% were
In the U.S., broadcasters and receiver manufacturers have agreed on a standard of  525 horizontal lines per frame MORE FRAMES/SEC LESS FLICKER
In order to work TV receivers require a source of field timing reference signals. These are signals that tell the TV receiver to be ready to receive the next picture in the stream of images. Early set designers decided to use the Mains power supply frequency as this source for two good reasons.
1 Older types of power supply, you would get rolling hum bars on the TV picture if the mains supply and power source were not at exactly the same frequency.
2.  TV studios would have had enormous problems with flicker on their cameras when making programmes. A frequency of 30 frames per sec. ( From the mains frequency)
Pixels per line is limited by the frequency channels allocated to television to about 330 elements per line.
The result is an image that consists of about 173,000 individual elements for the entire frame
In addition to standard combinations of Scan Rate, Colour System and transmission frequencies, there are further complications when it comes to additional features like Stereo Sound, Sub-titling and information services. Fortunately, such differences do not effect the basic operation of equipment conforming to the same broadcast standard, but they can restrict the use of various features.