Outline of the reasons social stratification is unavoidable according to the davis-moore thesis all positions in society must be filled. some positions are less important than others. more important positions must offer higher pay to attract qualified people. what is missing from the outline of the davis-moore thesis?

1. The reason why stratification is Unavoidable is: Some positions are less important than others. 
These positions often do not require any expertise and only took a little time for workers to train. It is unfair if the benefit for the workers to do this job is the same as the people whose job requires a certain expertise and took years to master.

2. What missing from the outline is that even if the job is considered as 'less important' people who held the 'more important' jobs tend to unable to do their job without the work result of people with 'less important job'.
Example: Managers wouldn't be able to maintain operation under the budget if the cashiers do not handle their station properly.

What kind of thing are you talking about? is it a book or a text? if it is what is the name?