Simply not true. Poorer households give a larger proportion of their income.

> It is clear from the graph that when put in the context of their individual budgets, donor households towards the lower end of the expenditure distribution tend to give away more of their money to charity than donor households in the higher expenditure percentiles. On this measure, poorer donor households are more generous than richer donor households, those in the bottom decile donating approximately 3% of their budget compared with those in the top decile donating roughly 1%.

http://www.cgap.org.uk/uploads/Briefing%20Papers/CGAP%20BN7%...