That target hasn't been hit consistently since the 1960s, when technology was providing big advancements, the workforce was younger and there was increased demand for American products worldwide as other countries fully recovered from World War II.
In the 1960s technology was just surfacing. Times seemed to be a tad easier during this time because of the technology that didn't exist. I think this is an unfair statement to compare the target of economic growth then and now due to the lack of motivation for the younger generation has for working. It seems that more of the younger people had more motivation to go out and have a job back then but now it seems to be easier to just file for unemployment or to be put on welfare then rather finding a job. Generation change is something that is big in this statement just because of the way that times have changed.