Just to throw a concrete number on this, extrapolating from Wikipedia, about $350k family income will put you above the 1% mark. I assume IPO-windfall would be considerably higher than that and maybe be at least top 0.1% that year ($2M+), which would be a different discussion.

So, mathematically, the number must lie between 1% and 30% that will be in the top 1% over a 30 year career. The question that remains is where in that range, which gives a measure of economic mobility for a country.