Before you make way too much fuzz over Slovakia - the figure is totally and utterly wrong! The decrease is 38. Check the YB and you'll see. So no -10,038 but only -38.
So a lot of pet theories will have to be stovced away, I am sorry. :-)
A thing infrequently mentioned, is the massive exodus of particularly men aged 20 thru 40 from all the East European countries to Western Europe in search of jobs. Poland, Lithuania, Latvia, Estonia, Slovakia, Rumania, Bulgaria in particular lose a lot of their male and young population each year.