What about a guy, who made 100 losing bets of small amounts of money and only one extremely lucky bet that won 10x or more? Assuming that he made more money with that bet than the money he lost. Does this make him a successful gambler or a loser? Maybe he sees himself as a winner, while in reality he's a loser, who happened to be extremely lucky for once.
I also think that many sports bettors are exaggerating their success so this survey can't be accurate.
Why aren't other European countries included? Football betting is very popular in my country. The TV shows are full with football betting ads.