I think it has more to do with culture than police effectiveness as we are not so popular as a country with good enforcement of law. Croatia is a small country and there is always someone that knows someone even if he is on the other side of the country. So even if somebody steals something from someone, there is a big chance that it is someone you know (he knows when you leave your house, when you get back etc.), so it would be a really big shame if you find out that someone you know stole something from you. Therefore, most thefts are done by Roma people because they are somewhat excluded/isolated from society.
Sounds horrible and for me it is unimaginable. In Croatia, you rarely hear that a car waa broken into even in bigger cities. In smaller towns a lot of people don't even bother to lock their cars.
Only 5 years sounds too good to me. In Zagreb, average price per m2 is about 2000 eur, and average monthly salary (in Zagreb) is little bit more than 1000eur which ia about 12000 eur per year. If you manage to save 20% you can get small 30m2 apartment in 25 years but most people go with credit loans which makes full repayment even longer.
Same happened to Croatia. From 2013. when we joined EU, Croatia lost at least 140000 people, which is about 3,3% of population, but unlike Bulgaria, I can say that Croatia is a really safe country.