Since fixed pricing was introduced in 2008, take up of pricing has been high. Around 80 per cent of pricing is now done prior to the start of the crush each season (based on a three million tonne crop). This 80 per cent includes around 50 per cent fixed pricing done by industry as part of Pricing Platforms, MITI and US Quota pricing of around 10 per cent and Seasonal Pool pricing of 20 per cent.

请问  这里面的seasonal pool  怎样理解