The assignment of factors is given as follows:
us_death_rate = sum(pop.column('2017')) us_death_rate.
An assignment refers to a statement that is used to appropriate value to a variable name.
In the question above, the variable name is us_birth_rate,
The value is "the total US annual birth rate in 2017".
The equal sign (=) is used as an operator to execute the assignment.
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