I am not familiar with that statistic. I could be based on how dirt poor the immigrants are (they may move up to how poor our poor are from mud-huts?), the fact that to get statistics you may be dealing with legal immigrants who often are the elite from other countries coming here to earn wealth, but...I've seen many studies that show people on welfare typically are on it for short periods of time and that a very small minority stays on for long but I'm not sure that addresses the poor as a whole.