# 2015-16 taxstats miscellany

#### Hugh Parsonage

#### 2020-07-13

    library(data.table)
    library(hutils)
    library(magrittr)
    library(ggplot2)

    library(grattan)  # needs to be before require_taxstats.
    has_taxstats <-
      require_taxstats() &&
      require_taxstats1516()

    s1516 <-
      as.data.table(sample_file_1516_synth) %>%
      setkey(Taxable_Income) %>%
      mutate_ntile("Taxable_Income", n = 100L) %>%
      mutate_ntile("Taxable_Income", n = 10L)
    s1516[, tax := income_tax(Taxable_Income, "2015-16", .dots.ATO = .SD)]

## Negative gearing

### Tax benefits

    s1516[, taxNoNG := income_tax(Taxable_Income - pminC(Net_rent_amt, 0),
                                  fy.year = "2015-16",
                                  .dots.ATO = .SD)]
    s1516[, benefit_due_NG := taxNoNG - tax]

#### by decile

    benefitsNG_by_Decile <-
      s1516[, .(avgBenefitNG = mean(benefit_due_NG)), keyby = "Taxable_IncomeDecile"]

    copy(benefitsNG_by_Decile) %>%
      setnames("Taxable_IncomeDecile", "Taxable Income Decile") %>%
      .[, Share := paste0(round(100 * avgBenefitNG / sum(avgBenefitNG)), "%")] %>%
      .[, avgBenefitNG := round(avgBenefitNG, -2)] %>%
      setnames("avgBenefitNG", "Average benefit from NG / $") %>%
      kable(align = "rrr")

### Average taxable income, by age and gender, 2015

    s1516[, .(avgTaxableIncome = mean(Taxable_Income)), keyby = .(age_range, Gender)] %>%
      .[age_range_decoder, on = "age_range"] %>%
      .[, Sex := if_else(Gender == 1, "Female", "Male")] %>%
      ggplot(aes(x = age_range_description,
                 y = avgTaxableIncome,
                 group = Sex,
                 color = Sex)) +
      geom_line() +
      scale_y_continuous(labels = function(x) paste0("$", prettyNum(x, big.mark = ",")))