You’re encouraged, but also overwhelmed: a single job posting has brought in hundreds of applications. Executives are so busy they can barely find time to sort through the most qualified candidates — and it’s doubly frustrating when less than 10 percent of applicants are qualified for the role. What’s going on? Where’s the top talent?

If this scenario sounds familiar, you may need the expertise of a recruitment firm to improve your hiring strategy. Internal recruiters can be effective, but they often have their hands full with ongoing cases; time is tight, and reaching out to passive candidates might be an unreasonable expectation for them. As a result, job boards are the default option.

Research suggests that job boards account for around 60 percent of all applications that a company might receive in response to a posting, which is more than any other platform or channel. However, conversion-to-hire rates for job boards are nowhere near those of referrals or company websites.

Despite attracting the most applicants, only 15 percent of candidates applying through job boards actually get hired, whereas close to 50 percent of employee referrals are hired. That means that people being are hired elsewhere through referrals or company career sites before your job post ever goes live.

Aside from these statistics, here are four additional reasons why job postings just aren’t enough to find good candidates.

1. Internal HR Processes Can be Inefficient

Yes, job postings yield hundreds of applicants on average, but even the most talented recruiters and human resources managers can miss things when they’re trying to fill multiple positions — even upwards of fifty at one time. They’re responsible for managing the expectations of hiring managers, reading through resumes, scheduling interviews, and playing an active role throughout the screening process. It can be overwhelming, which makes it difficult to avoid overlooking qualified applicants.

2. Job Postings Don’t Attract All the Qualified Talent

Let’s face it: top talent isn’t cold calling companies or browsing job boards. People with in-demand skills are likely to be gainfully employed already, not actively looking for new positions.

But that doesn’t mean that they aren’t networking or keeping their eyes on LinkedIn and other social media for exciting new opportunities. One-third of the workforce is active talent, according to the 2015 Global Talent Trends report, and that group is likely to see your job posting. However, that leaves the remaining 70 percent, who won’t see your posting because they aren’t actively looking.

Why try to reach that 70 percent if they’re already satisfied? Though they may not be looking today, they very well could begin looking tomorrow. In other words, if a talented candidate knows you’re hiring even when they aren’t available, they might seek you out when they are.

3. Passive, Qualified Candidates Like Recruiters

Recruiters know the market and are therefore able to establish long-term relationships with clients. They start conversations with people when they aren’t necessarily job seeking so that they will reach out to the recruiter when they’re ready to start an active search. Many qualified, niche candidates will contact a recruiter rather than browsing job boards when they decide to dip their toes in the job pool.

4. Job Postings Are Reactive, Not Proactive

Job postings have value in terms of SEO, and active candidates searching for a job may pull up your job description that way. However, waiting for applicants to find you and then qualifying received applications against a job description is both time-consuming and inefficient. Instead, follow the example of marketers: reach out to potential candidates before your competitors do.

For example, expert coders are often difficult to hire, but Google and other tech companies are reaching out to them where they are likely to hang out: on websites popular with the coding community. Google often hosts competitions for coders, which have the added benefit of helping Google assess who has talent and who doesn’t.

The bottom line is that recruiting top talent is a lot like marketing: it requires building a reputation as an employee-oriented organization, utilizing targeted outreach efforts through appropriate channels, and understanding the labor market. And just as many companies turn to marketing firms with the right tools and strategies, the savviest companies rely on recruitment agencies to hire employees they know will be an asset to their organization.