<p>“The number of bachelors degrees is the total over three years 2002-2004 in engineering”</p>
<p>IMO you ought to be using bachelors degrees for a period lagging the years for PhD degrees, by about five years or so.</p>
<p>For example, I’m pretty sure my own alma mater substantially increased its undergraduate engineering enrollment during this period. So if you compare its Phds from 1995 in numerator, but use its undergrad class size from 2002 in the denominator, instead of the size of the class of 1990 that more likely produced these particular PhDs, you may be materially understating the actual % pHDs that emanated from this one school.</p>