W A T W A S T E r , t = S A N I T A T I O N ( i m p r o v e d ) r , t 1 + e − ( − 2.4 + 0.043 ∗ G D P P C P r , t + 0.042 ∗ P O P U R B A N r , t P O P r , t ) {\displaystyle WATWASTE_{r,t}={\frac {SANITATION(improved)_{r,t}}{1+e^{-(-2.4+0.043*GDPPCP_{r,t}+0.042*{\frac {POPURBAN_{r,t}}{POP_{r,t}}})}}}}