The table shows the amount of direct tax paid by individuals at different levels of income in a country.
| Annual income (£) | Direct tax paid (£) |
|---|---|
| 15 000 | 1 500 |
| 30 000 | 3 000 |
| 45 000 | 6 750 |
Which of the following statements about the country's direct tax system is true?
The system is progressive throughout the income range
The system is proportional from £15 000 to £30 000 only
The system is proportional throughout the income range
The system is regressive between £30 000 and £45 000
