A researcher is conducting a survey to estimate the proportion $p$ of city residents who support a new bike lane. They decide to use a stratified random sample with proportional allocation based on three city districts. If the total population size is $N = 5000$, and the district populations are $N_1 = 2500$, $N_2 = 1500$, and $N_3 = 1000$, what is the sampling weight $w_i$ for each district if the total sample size is $n = 500$?