The constant of proportionality in a direct variation equation of the form \( y = kx \), where \( k \) is the constant of proportionality, indicates how \( y \) changes with \( x \).
In the equation \( y = 2 \frac{2}{3} x \), we can convert \( 2 \frac{2}{3} \) to an improper fraction:
\[ 2 \frac{2}{3} = \frac{8}{3} \]
Thus, the equation can be rewritten as:
\[ y = \frac{8}{3} x \]
The constant of proportionality is \( \frac{8}{3} \).