A new research paper suggests potential employers think less of unemployed job candidates no matter how briefly they've been out of work. And it doesn't matter whether workers quit voluntarily or were laid off through no fault of their own.

"Although it has long been theorized that the simple fact of being unemployed carries a stigma, the idea has never really been tested outside some studies by economists who have focused on the duration issue," said Geoffrey C. Ho, a doctoral candidate at the UCLA Anderson School of Management who co-authored the article.

"We found bias against the jobless, among human-resource professionals as well as among the broader public, virtually from the outset of unemployment," Ho said.

More than 5 million Americans have been unemployed for six months or longer.

In one study, Ho and his team asked 47 experienced HR professionals to review resumes that were identical except for one detail: Half said the candidate was currently employed, and half said the person had been out of work for a month. The "currently employed" candidate received better marks for competence and hireability.

In another experiment, researchers asked a group of students to review identical resumes from "employed" and "unemployed" job candidates, with the latter group divided between people who'd left their jobs voluntary and people who'd been let go. The "laid off" crowd fared no better than the quitters.

"Those two words by themselves don't elicit any more sympathy than 'left voluntarily,'" Ho said.

He noted that a third experiment found that job candidates whose previous employer went under received more sympathy. "What does allay people's bias is some explicit indication that losing your job was not your fault -- for example, that the company went bankrupt or suffered some specific setbacks that made layoffs inevitable," Ho said.

HuffPost readers: Coping with unemployment? Tell us about it -- email arthur@huffingtonpost.com. Please include your phone number if you're willing to be interviewed for a future story.

Ho conducted the research with Margaret Shih and Daniel J. Walters of UCLA Anderson and Todd Lowell Pittinsky of Stony Brook University. Their article, titled "The Psychological Stigma of Unemployment: When Joblessness leads to Being Jobless," will be published among thousands of other papers at the annual meeting of the Academy of Management on Aug. 5.

Lawmakers in several states proposed prohibiting employers from discriminating against unemployed candidates in 2010, in response to news stories about job listings that specified candidates "must be currently employed." President Barack Obama proposed banning such discrimination in 2011.

The Congressional Budget Office has estimated that the stigma of unemployment has boosted the national jobless rate by a quarter of a percentage point.

To illustrate "a psychological stigma against the unemployed," the new research paper's epigraph is a line from a piece Ben Stein wrote for the conservative American Spectator in 2010: "The people who have been laid off and cannot find work are generally people with poor work habits and poor personalities."

Below are the companies with the toughest interviews:
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  • Amazon

    Interview Difficulty Rating: 3.3 Employee Satisfaction: 3.3 "If you were to rank quality, customer satisfaction, and safety in order of importance, how would you rank them? Discuss." -Amazon Area Manager Candidate (Allentown, PA)

  • Facebook

    Interview Difficulty Rating: 3.3 Employee Satisfaction: 4.6 "It's 6pm and your work day is over, what happened during the day that made it awesome?" -Facebook Account Manager Candidate (Austin, TX)

  • Headstrong

    Interview Difficulty Rating: 3.3 Employee Satisfaction: 2.9 "If your parents are doctors why didn't you become one?" -Headstrong Associate Engineer Candidate (Delhi, India)

  • Progressive Corporation

    Interview Difficulty Rating: 3.3 Employee Satisfaction: 3.6 "Tell me about a time when you changed the culture in the workplace." -Progressive Corporation Claims Generalist Candidate (Des Moines, IA)

  • General Mills

    Interview Difficulty Rating: 3.3 Employee Satisfaction: 3.8 "If you had $5,000, who would you invest in and why?" -General Mills Intern Candidate (location n/a)

  • Stryker

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.2 "Would you rather be the best? Or do your best?" -Stryker Design Engineer Candidate (location n/a)

  • Sapient

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.3 "How to arrange 9 balls in minimum attempts?" -Sapient Global Markets QA Candidate (location n/a)

  • Juniper Networks

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.3 "What were you least favorite subject(s) during school and why?" -Juniper Industries Marketing Coordinator Candidate (Middle Village, NY)

  • LEK Consulting

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.4 "Estimate the annual revenue of a multiscreen cinema? Try 2 different methods" -L.E.K. Consulting Life Science Associate Candidate (London, England)

  • Teach For America

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.7 "What would cause you to want to dropout of Teach For America if you were chosen?" -Teach For America Corps Member Candidate (location n/a)

  • Proctor & Gamble

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.8 "Describe a situation in your life in which you feel had the most important effect on your life today and the values you follow" -Procter & Gamble Intern Candidate (Jackson, TN)

  • Bazaarvoice

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.2 "Tell me about your sense of humor." -Bazaarvoice Customer Service Manager Candidate (Austin, TX)

  • Susquehanna International Group

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.7 "The chance it'll rain in the next hour is 84%. What is the chance it'll rain in the next half hour?" -Susquehanna International Group Assistant Trader Candidate (Philadelphia, PA)

  • Cypress Semiconductor

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 2.9 "How many gas stations are there in SF?" -Cypress Semiconductor Product Engineer Candidate (San Jose, CA)

  • Rackspace Hosting

    Interview Difficulty Rating: 3.4 Employee Satisfaction: 3.9 "Name as many uses for a brick as you can in 1 minute." -Rackspace Linux Systems Administrator Candidate (San Antonio, TX)

  • Interview Difficulty Rating: 3.5 Employee Satisfaction: 3.1 "What is more necessary, skill or will?" -Unisys Systems Analyst Candidate (Bangalore, India)

  • Google

    Interview Difficulty Rating: 3.5 Employee Satisfaction: 4.1 "How many hotels are there in the US?" - Google Product Manager Candidate (Mountain View, CA)

  • Shell

    Interview Difficulty Rating: 3.6 Employee Satisfaction: 3.8 "Give 2-3 negative points of diversity in a company" -Shell Oil Supply Chain Graduate Candidate (location n/a)

  • Bain & Company

    Interview Difficulty Rating: 3.6 Employee Satisfaction: 4.2 "Estimate how many windows are in New York" -Bain & Company Associate Consultant Candidate (Boston, MA)

  • ThoughtWorks

    Interview Difficulty Rating: 3.6 Employee Satisfaction: 3.8 "Interview me and then tell me, if you would hire me" - ThoughtWorks Talent Scout Candidate (Porto Alegre, Brazil)

  • ZS Associates

    Interview Difficulty Rating: 3.7 Employee Satisfaction: 3.4 "A pharma company you are consulting is coming up with 2 new products. What factors would help them decide how to distribute their sales force?" -ZS Associates Associate Candidate (San Mateo, CA)

  • ATKearney

    Interview Difficulty Rating: 3.7 Employee Satisfaction: 3.4 "After streamlining and reducing purchasing cost for raw materials, can you think of another way to reduce the cost of making a piece of chocolate?" - A.T. Kearney Business Analyst Candidate (location n/a)

  • Oliver Wyman

    Interview Difficulty Rating: 3.7 Employee Satisfaction: 3.6 "What is the profit potential of offering wireless internet service on planes?" - Oliver Wyman Consultant Candidate (location n/a)

  • Boston Consulting Group

    Interview Difficulty Rating: 3.8 Employee Satisfaction: 4.1 "How many people would use a drug that prevents baldness?" - Boston Consulting Group Associate Candidate (Boston, MA)

  • McKinsey&Company

    Interview Difficulty Rating: 3.9 Employee Satisfaction: 4.1 "There are 3 products: tomatoes, luxury cars, t-shirts. What value added tax is applied to each product type?" - McKinsey & Company Junior Consultant Candidate (location n/a)