That holds until the cross-over point where the unemployed half is larger than the employed one.
Note that most unemployment statistics define unemployment as a subset of the whole population that both has no job and is not actively seeking one. That last criteria is rarely as objective as the first one.
In Greece, unemployment is currently 25% or so. 48.6% for 18-25.
There were 3,644,000 employed individuals as of july 2015. For a total population close to 10.8m. Employed people are far from the "largest half."
For the US, from the same source (all number Sep 2015), the numbers are:
Unemployment: 5.1% (Youth: 11%)
148,800,000 employed individuals out of 319m population... So 160+m people are not seeking work either because they're kids, retired, unable to work, inmates or have given up.
Source: http://www.tradingeconomics.com/greece/unemployment-rate