Hate to tell you but the unemployment rate is not an accurate measure since it doesn't include discouraged workers, marginally attached workers, or the long-term unemployed. There is no differentiation on part-time vs. full-time which is why you hear of so many people with two or three part-time jobs trying to make ends meet. And it doesn't include if those jobs are getting people to minimal standards of survival.
So yeah, 4% looks great but the there is evidence the actual rate is about 24% in the US.
Then add in the long-standing manipulation of job offers by companies that are trying to maintain stock price (hey look, we're hiring! we're great!), or trying to improve morale internally (hey, keep killing yourself for the company, help is coming, see this listing for a new hire that's been posted every three months for a year or two??), or are looking to go public. There are the ones that are done by companies with no intention of hiring externally but have to be offered by employment law or personnel contracts to external individuals first (hey, see this amazing listing for requirements that don't actually exist!) and are being "budgeted" to be not filled so the company doesn't have the expense for the posting until the new year.