Here is my explanation:-
Correlation is between high voter turn and total taxable income. Mayor proposed to increase minimum wage, thinking it will increase total taxable income and in turn more voter turn out.
But think of some scenario in which this doesn't hold true. Scenarios in which increasing a minimum wage, will not in turn increase total taxable income. Some scenarios are mentioned below :-
1. What if increased wage will have an effect on employment rate. Increasing wage will reduce the employed people , in turn can bring down or same as per current level of total taxable income.
2. What if all the employed people is earning way above the minimum wage, this will not have any effect on total taxable income.
Scenarios like these will weaken the argument, hence we need to find just opposite of these scenarios.
for 1. The employment rate in Sleepy Valley will not decrease.
2. There are some people who will benefit from increase in minimum wage, while rest will not be affected by this minimum wage increase.
So and choice C suits and seems correct ans to me.
(A) The proportion of registered voters to taxpayers in Sleepy Valley is greater than the proportion of registered voters to taxpayers nationally.
Out of Scope as we don't care about the comparison between sleepy valley and nation wide.
(B) Almost all registered voters are taxpayers.
Doesn't matter as the correlation will still hold.
(D) Most taxpayers in Sleepy Valley have little or no earned income.
But how increase in minimum wage will effect to people who has some income. Will that increase overall taxable income? we dont know.
(E) Most of the taxpayers who are not registered voters in Sleepy Valley earn more than minimum wage.
This option only talks about taxpayers who are not registered, lets say this group as A and another group B i.e. Taxpayers who are registered. So clearly Group A will not affect the total taxable income, but what about group B, we dont know. Will that increase total taxable income or reduce, we dont know. It depends how the group is affected. Hence E is also out.