Taking the analysis a stage further and fitting a linear regression model of seaborne
imports on GNP (see graph inset) we find that 71% of the variation in seaborne
imports is explained by variations in GNP (this is R2). The model implies that in 2004
seaborne imports start when
GNP reaches $60 billion and
increase by 110,500 tons for each
$1 billion increase in GNP.