Update: Added a significant part to the start of this answer to clarify the question. The big point here is that less than 1-in-5 low-income Americans didn't vote compared to the average American. This answer explains that disaffect is the primary cause for these less-than-1-in-5 (~18.5%). ###Clarifying the question, Part 1: Only 30% less likely to vote This
Clarifying the question, Part 1: Only 30% less likely to vote
This question's source gets its information from a graph in this report:
###Clarifying the question, Part 2: We're talking about 1/3 of the non-voting low-income Americans
Clarifying the question, Part 2: We're talking about 1/3 of the non-voting low-income Americans
###Clarifying the question, Part 3: Low-income Americans are a diverse group
Clarifying the question, Part 3: Low-income Americans are a diverse group
Bystanders, Disaffecteds, and Hard-Pressed Skeptics
###Bystanders, Disaffecteds, and Hard-Pressed Skeptics StudiesStudies have shown that significant portions of the population are disaffected. They don't tend to make much money, and they're generally not too interested in politics. The central point of this answer is that they're a large enough group to explain much of the small disparity in voting rates between low-income earners and the average American.
Not work-scheduling problems
###Not work-scheduling problems ReferringReferring to the above graph that the numbers in the question come from, people who made less than $10,000/yr had the same voting rate as people who made $10,000-$15,000/yr. Minimum wage laws mean that no one regularly working full-time or near-full-time can fall into this category.
Comments
###Comments ThisThis issue's fairly sad because it largely observes that a significant portion of the population's given up. This is a harder issue to fix than other proposals like limited access to the polls or work conflicts.