As you might imagine, this is a contentious subject. The Brennan Center did a thorough study in 2006, and while a bit dated now, here’s what they found:
As many as 11 percent of United States citizens – more than 21 million individuals – do
not have government-issued photo identification.
Elderly citizens are less likely to possess government-issued photo identification.
Minority citizens are less likely to possess government-issued photo identification.
Citizens with comparatively low incomes are less likely to possess photo identification.
Photo identification often does not reflect current information.
As for being able to get an ID:
As many as 7% of United States citizens – 13 million individuals – do not have ready
access to citizenship documents.
Citizens with comparatively low incomes are less likely to possess documentation
proving their citizenship.
Documentation proving citizenship often does not reflect the citizen’s current name.
It is difficult to believe, until you consider that lawmakers might go out of their way to make it as inconvenient for poor folks as possible. Again from a Brennan Center study:
"The 11 percent of eligible voters who lack the required photo ID must travel to a designated government office to obtain one. Yet many citizens will have trouble making this trip. In the 10 states with restrictive voter ID laws:
–Nearly 500,000 eligible voters do not have access to a vehicle and live more than 10 miles from the nearest state ID-issuing office open more than two days a week. Many of them live in rural areas with dwindling public transportation options.
–More than 10 million eligible voters live more than 10 miles from their nearest state ID-issuing office open more than two days a week.
–1.2 million eligible black voters and 500,000 eligible Hispanic voters live more than 10 miles from their nearest ID-issuing office open more than two days a week. People of color are more likely to be disenfranchised by these laws since they are less likely to have photo ID than the general population.
–Many ID-issuing offices maintain limited business hours. For example, the office in Sauk City, Wisconsin is open only on the fifth Wednesday of any month. But only four months in 2012 — February, May, August, and October — have five Wednesdays. In other states — Alabama, Georgia, Mississippi, and Texas — many part-time ID-issuing offices are in the rural regions with the highest concentrations of people of color and people in poverty.
More than 1 million eligible voters in these states fall below the federal poverty line and live more than 10 miles from their nearest ID-issuing office open more than two days a week. These voters may be particularly affected by the significant costs of the documentation required to obtain a photo ID. Birth certificates can cost between $8 and $25. Marriage licenses, required for married women whose birth certificates include a maiden name, can cost between $8 and $20. By comparison, the notorious poll tax — outlawed during the civil rights era — cost $10.64 in current dollars."
This is like asking, how do we know with certainty that there aren’t little green men living on Mars? The short answer is, we can never answer in the negative with utter certainty. Re Mars-men, all we can say is we’ve examined the planet carefully, and thus far haven’t turned up any evidence suggestive of their existence. Likewise, regarding in-person voter fraud, all we can say is we’ve scoured the country for many years looking for it, and have come up with something like 13 confirmed cases out of ~1 billion votes cast.
Not for the unemployed, or for those working in the underground economy (think maids, yard men, sitters, etc).
Some states have ID’s just for the purpose of voting and they’re free.