Finding a job is hard work. You have to find opportunities that match your skills and interests, painstakingly prepare resumes and cover letters, and hone your interviewing skills. Once you’ve done all that, why are most applications still unanswered and actual job offers so scarce?

Sometimes it’s because there are things going on behind the scenes that are conspiring against you – that you will probably never find out about. Here are five hidden reasons why you might not get hired, that employers won’t tell you.

1. If you get on their nerves, they can (and will) blacklist you from future opportunities.

The biggest pet peeve of hiring managers is receiving applications from candidates who are just not relevant or qualified for the job they are hiring for. A recent survey of 1,500 recruiters and hiring managers found that such unrelated applications was the biggest turnoff for 30% of them. (And of that group, 43% said they would go so far as to ‘blacklist’ those candidates from any other jobs as well – by suppressing their names from even coming up in future searches.)

Other candidate behaviours that annoy recruiters include exaggerating your qualifications, focussing on the salary more than the job, and following up too often on your application. (More than once a week is bad.)

2. The resume that you spent hours perfecting gets very little attention.

More and more companies – especially the larger ones – are using software that filters through applications before a recruiter or hiring manager even sees them. If your resume doesn’t contain exactly the relevant keywords that are being screened for, you won’t make the cut. Many, if not most, resumes get rejected before anyone even takes the time to read them. See: The exact resume keywords employers search for by industry

Oh, and when your resume does manage to land in front of a real person, they spend less than 11 seconds reading it before deciding to shortlist it or toss it. Workopolis can see in real-time how many resumes employers look at, and how long they spend on each resume page before saving it or moving on. In less than 11 seconds, 80% of that fraction of the resumes that survive the keyword scan are rejected.

Perhaps that’s why only 2% of applicants are even selected for interviews.

3. Employers judge you within mere seconds of meeting you.

It’s true. Important decisions about your candidacy are made in the first few crucial seconds of a job interview. Pre-reflective assumptions can set the mood of the rest of your interview – and they can be hard to turn around.

This is because in the first four seconds of meeting someone we decide four things about them: Do I like them? Do I trust them? Are they safe? Who do they remind me of?

Your chances of landing the job can be sunk just because you bear a passing resemblance to the bully who used to pick on the hiring manager in high school.

With that in mind, here are some strategies you can use to give you every chance of acing (or recovering from) that first impression.

4. They talk behind your back and cyberstalk you.

Employers don’t limit their background checks to those three carefully chosen references that you’ve coached to sing your praises. They will ask around to see if anyone in their network has worked with you before – or knows anyone at one of your previous employers. So someone you didn’t get along with who only worked with you in a peripheral manner could still be influencing your success years later.

Employers will also be Goggling you, looking you up on Facebook and Twitter and they will be judging you by what the find. 42% of those surveyed say that they have changed their minds about whether or not to hire someone based on what they have found online. (And if they can’t find you at all, you can be judged poorly for that too.)

Here’s what they want to see.

5. They prefer employed candidates.

It’s not fair, but the bias exists. Some employers think that employed candidates are more valuable than unemployed candidates. There is always the chance that unemployed candidates are out of work through some failing in their skills, work-ethic, or personality. (Now this is not a fair assumption, and it’s usually not the case, especially in a tight job market like we have seen in any parts of the country since the recession, but it is something that crosses the minds of some hiring managers.)

While you’re currently employed, someone out there is already willing to pay you for what you do. It’s an unspoken recommendation from one employer to another. If you’re out of work – they think – there’s the possibility that the problem is you. Unfortunately the longer you go between jobs, the worse this perception can get.

This is why I recently wrote “The best time to quit your job.” (It’s when you’ve already lined up your next one.)