n-affected-by-div293.R

library(taxstats)
library(grattan)
library(data.table)
library(dplyr)
library(magrittr)

n_affected_by_div293 <-  function(div293.threshold = 300e3, cap = 30000, cap2 = 35000, age_based_cap = TRUE, div293 = TRUE,  super.guarantee.rate = 0.095, use.sample.file = "2013-14", h = 0L){
  sample_file_extended <- 
    # sample_files_all[fy.year == use.sample.file] %>%
    sample_file_1314 %>%
    project(h = h) %>%
    # 50 year olds and over get a cap of 35e3
    mutate(prev_cap = ifelse(age_range <= 4, 35e3, 30e3)) %>%
    mutate(
      # Throughout we assume that the minimum amount of super guarantee contributions are made. 
      super_income_in_excess_of_cap = pmax(0, Rptbl_Empr_spr_cont_amt + Non_emp_spr_amt + super.guarantee.rate * Sw_amt - prev_cap),
      # the minimum of the cap applicable or the contributions actually made
      prv_concess_contr_amt = pmin(prev_cap, Rptbl_Empr_spr_cont_amt + Non_emp_spr_amt + super.guarantee.rate * Sw_amt),
      new_concess_contr_amt = pmin(ifelse(age_range <= 4, 
                                          ifelse(age_based_cap, cap2, cap), 
                                          cap), 
                                   #
                                   Rptbl_Empr_spr_cont_amt + Non_emp_spr_amt + super.guarantee.rate * Sw_amt),
      new_super_income_in_excess_of_cap = pmax(0, Rptbl_Empr_spr_cont_amt + Non_emp_spr_amt + super.guarantee.rate * Sw_amt - ifelse(age_range <= 4, if(age_based_cap) cap2 else cap, cap)),
      
      new_Taxable_Income = Taxable_Income - super_income_in_excess_of_cap + new_super_income_in_excess_of_cap,
      #
      revenue_due_to_Taxable_Income = income_tax(new_Taxable_Income, 
                                                 fy.year = use.sample.file) - income_tax(Taxable_Income, 
                                                                                         fy.year = use.sample.file)
    ) %>%
  # div293
      mutate(
        prv_tax_payable_on_concess_contr = 0.15 * prv_concess_contr_amt,
        new_tax_payable_on_concess_contr = 0.15 * new_concess_contr_amt,
        
        # https://www.ato.gov.au/uploadedFiles/Content/TPALS/downloads/Division-293-scenario-table-v2.pdf
        # Technically the surchargeable income includes amounts on which family trust distribution tax has been paid. This has
        # been omitted, meaning that some individuals' div 293 tax burden is underestimated.
        prv_surchargeable_income293 = Taxable_Income + Net_fincl_invstmt_lss_amt - pmin(Net_rent_amt, 0) + Rep_frng_ben_amt,
        # We assume that low tax contributions cannot be negative. Since prv concess is capped, 
        # we don't have to subtract off excess contributions
        prv_low_tax_contributions293 = pmax(0, prv_concess_contr_amt),
        prv_div293_income = prv_surchargeable_income293 + prv_low_tax_contributions293,
        prv_div293_tax = ifelse(prv_div293_income > 300e3, 
                                0.15 * pmin(prv_low_tax_contributions293, 
                                            pmax(prv_div293_income - 300e3, 0)),
                                0),
        
        new_surchargeable_income293 = new_Taxable_Income + Net_fincl_invstmt_lss_amt - pmin(Net_rent_amt, 0) + Rep_frng_ben_amt,
        new_low_tax_contributions293 = pmax(0, new_concess_contr_amt),
        new_div293_income = new_surchargeable_income293 + new_low_tax_contributions293,
        new_div293_tax = ifelse(new_div293_income > div293.threshold, 
                                0.15 * pmin(new_low_tax_contributions293, 
                                            pmax(new_div293_income - div293.threshold, 0)),
                                0)
      )
  
  n_affected <- 
    sample_file_extended %$%
    sum((new_div293_tax > prv_div293_tax) * WEIGHT)
  
  n_affected
}