UK vs SG income tax for the salary man

Source:

• https://www.iras.gov.sg/taxes/individual-income-tax/basics-of-individual-income-tax/tax-residency-and-tax-rates/individual-income-tax-rates
• https://www.gov.uk/government/publications/rates-and-allowances-income-tax/income-tax-rates-and-allowances-current-and-past

I assumed the exchange rate of 1 GBP to 1.7 SGD.

GnuPlot script:

set terminal pngcairo size 1024,768 enhanced font 'Verdana,10'
set output 'tax_bands.png'

set datafile separator comma
set key left top
set title "Tax Bands: SG vs UK"
set xlabel "Threshold in SGD"
set ylabel "Tax Rate (%)"
set grid
set xrange [0:300000]
set yrange [0:50]
set xtics (0, 8500, 20000, 30000, 40000, 64090, 80000, 120000, 160000, 200000)
set xtics rotate by 90 right

# Define the data for Singapore
$sg_data << EOD
threshold in SGD,tax rate %
0,0
20000,2
30000,3.5
40000,7
80000,11.5
120000,15
160000,18
200000,19
280000,19.5
320000,22
500000,23
1000000,24
EOD

# 5000GBP * 1.7 = 8500SGD
$uk_data << EOD
threshold in SGD,tax rate %
0,0
8500,20
64090,40
212739,45
999999999,45 
EOD

plot $sg_data using 1:2 with steps title "Singapore" lt rgb "blue", \
     $uk_data using 1:2 with steps title "United Kingdom" lt rgb "red"

Any tips on how to improve this visualisation?