Many jobs ads make an effort to obscure salary information. They may say something like "salary commensurate with experience" or simply not say anything at all. In many cases, the employment listing tells job seekers that the salary is negotiable -- but a surprisingly small number of people actually bother to negotiate after being offered the job.

Only 39% of the more than 2,700 workers asked whether they tried to negotiate a higher salary when offered their last job said yes according to a new report from Robert Half, a staffing firm. More men (46%) tried to negotiate than women (34%), and younger workers aged 18-34 were more likely to negotiate (45%) than those aged 35-54 (40%) and those 55 or older (30%).

A chart of which workers negotiated salaries and which didn't.

Image source: Robert Half.

Why is this happening?

Obviously, in some cases, there are jobs where the salary is clearly stated going in. In other situations, the job seeker named a desired salary in a cover letter or elsewhere in an application before interview process began. If the company meets that number, it's hard for the prospective employee to ask for more.

A lot of workers, however, don't negotiate out of either fear or relief. Sometimes a job seeker is so happy to get the job he or she does not make sure to get paid the most money possible. In other cases, the person who got offered the job is afraid that negotiating may result in the offer being pulled.

No matter the reason, job seekers should speak up, according to Robert Half Senior Executive Director Paul McDonald. They should also do their homework and ask for a reasonable salary based on what the job should pay, not their own salary history.

"Starting salary should be a factor of the job skills required and current market demand for those skills," he said in a press release." That's why it's more important than ever for both parties to research market conditions thoroughly to pave the way for realistic, productive discussions."

McDonald also warned workers about two common pitfalls in the hiring process.

"First and foremost, avoid negotiating any part of the compensation package until after you've received a formal offer," he said. "Second, don't go into a negotiation without practicing the conversation in person with a trusted friend or mentor."

Two people shake hands while one hands money over to ther other.

Salary is often negotiable. Image source: Getty Images.

What should you do?

While it sounds nice to say you should stand up for yourself every time you get a job offer, the reality is that you have to consider your situation. Yes, you should know what comparable jobs pay and have as much information available to you as possible.

How hard you fight, however, depends upon your specific circumstances. If the offer is low, but you are desperate for work, you may want to consider accepting, but negotiating a time either three or six months down the road to revisit the salary. You may also want to negotiate non-monetary perks like time off. But if you really need the job -- or the offer is fair enough -- sometimes it's OK to not fight for every nickel.

If you have leverage (like another offer or a current job you'd be happy to stay in) negotiate and negotiate hard. When that's not the case, it generally does not hurt to ask for more as long as you do it respectfully. Stand up for yourself in a reasonable way and you may find the company willing to sweeten the deal in order to land your services.