Shaping, why does it make my internet slower?

In Australia, Internet Service Providers (ISPs) assign download quotas to their broadband packages. Having a broadband quota means there is a limit assigned to how much web activity you can undertake, e.g. how many web pages you can view, how many movies, songs and photos you can download or how many emails you can receive.
Once you reach your quota limit for the month, it is common practice for ISPs to charge excess usage fees. This means for every extra amount of data you download, you have to pay a fee which can quickly add up into a larger bill for your internet than you expect.
An alternative method is called shaping, which instead slows your internet speed right down when you reach your quota limit, rather than charging any extra fees. This seems like a fairer (and less costly method).
What is shaping? What happens when you exceed my quota?
Shaping is the term used to describe the slowing of a connection that has exceeded its allotted download allowance for a period. Some ISP broadband services are shaped to specific kilobytes per second, such as 64kbps, up and down for the period in which you have exceeded your quota.
At the end of your monthly cycle, the normal speeds of your broadband plan will resume and your quota will be reset. This method means that some internet service providers don't need to charge excess fees on their broadband plans. If the customer wants the internet service to be reshaped before the quota reset, they must upgrade to a better broadband plan.
What is generally counted towards a monthly quota?
Many internet service providers count both uploads and downloads towards allocated monthly quota, however some providers do offer quotas that constitute of downloads only.
How do you know when you quota is nearly up?
Firstly, a month is defined as the period between anniversary dates. You can check your quota limits by logging into your personal account, given by your ISP. It is recommended to keep an eye out on your quota each month to ensure you make the best use of your download limit.