The average US senior software engineer stays at the same company for 18 months. Not because they’re unhappy. Not because the work is bad. Because the market is liquid enough that a better offer is always one recruiter call away, and most companies have built their compensation structures around competing for new hires rather than retaining the engineers they already have. That 18-month number isn’t a surprise to anyone who has run an engineering organization. What is surprising is how few companies have actually priced it into their hiring math.
The vacancy cost nobody talks about
When a senior engineer leaves, the clock starts on a cost that never shows up cleanly on any budget line. The role sits open for an average of three to five months at the senior level — longer if you need domain-specific experience. During that window, the team absorbs the work, code reviews slow down, architectural decisions get deferred, and junior engineers lose the mentorship that was supposed to develop them into the next tier. None of that gets a line item. It just shows up as slower shipping, more bugs, and missed Q3 milestones.
Then the recruiter fee lands. For a senior engineer at $150–180K base, contingency recruiting fees typically run $30–45K. Add three months of reduced productivity, onboarding ramp of another two to three months before the new hire is actually contributing at full capacity, and you’re looking at a real cost of $80–120K per departure before the new engineer writes a single line of code that matters. At 18-month average tenure, that cycle repeats before the investment in the previous hire has paid back.
The pipeline was never built for senior roles
The US engineering talent pipeline produces a lot of junior and mid-level engineers. Bootcamps, CS programs, online certifications — the supply of people who can write code has grown significantly over the past decade. The supply of engineers who can design a distributed system, review a PR in a way that actually transfers knowledge, hold an opinionated architectural position under pressure, and do all of it reliably across a three-year arc has not grown at anything like the same rate. Senior engineers are made through time and practice, not curriculum. The pipeline just isn’t long enough to produce them at the rate the market demands.
The result is a market where senior engineers are permanently in short supply, have the leverage to job-hop at will, and receive competing offers constantly regardless of how well a company treats them. The market pays them to leave. CTOs know this, and most have quietly accepted it as a fixed cost of doing business. The ones who haven’t are the ones looking at the problem differently.
Why the usual fixes don’t work
The common responses to the retention problem — above-market raises, retention bonuses, accelerated vesting, culture initiatives — don’t change the underlying dynamic. They raise the floor, which raises the market, which raises the cost of the next offer. The engineer who takes a $30K retention bonus and leaves 10 months later for $40K more somewhere else isn’t acting irrationally. The market created that outcome. Companies trying to win a compensation arms race they can’t cap are running faster to stay in the same place.
The companies that have materially solved this are the ones that changed the talent pool rather than the compensation package. Remote-first hiring opens geographic arbitrage — not in the race-to-the-bottom sense, but in the sense that a senior engineer in Prague who is earning two to three times their local market rate has different reasons to stay than an engineer in San Francisco who can walk across the street for $30K more. The financial incentive to leave is smaller. The life context is different. The average engagement length is three to four years, not 18 months.
What this looks like in practice
A US company that places one senior Czech engineer at $100K annually instead of a US-based hire at $175K all-in total cost, and retains that engineer for three years instead of 18 months, saves roughly $350K over that window when you factor in the avoided recruiting cycle and ramp costs. That’s not a rounding error. It’s a mid-level engineering salary. The math only works if the engineer is actually senior — pre-vetted, technically strong, English-fluent, and capable of working independently in a US remote context. That’s not a guarantee with any source of talent. It’s the bar worth holding.
If you’re a CTO or VP of Engineering dealing with open senior roles, see the pre-vetted Czech and Slovak engineers currently available. Placement in 1–14 days. No fee until the engagement starts.