As mentioned, lowering the first tax rate will provide people with a bit of tax relief. They will pay less than what they would have been paying under the 15% rate.
In terms of economic impacts, that really depends on how people choose to use their savings, whether they are for additional savings or additional consumption. These are the two ways that economic growth could be stimulated. We don't have any particular projections on exactly what people's behavioural response to the rate change would be, but generally speaking these are the channels through which there would be economic impacts.