Combine old FAO fodder data (pre-2010 item codes, 1961-2011) with new Fodder2010 data (CPC codes, 2010-2023). The old data is kept up to its last year (2011), the new data is used afterwards. New items without an old equivalent are aggregated into the old item codes (see FodderItemMapping.csv). Old items without a new equivalent (648 Carrots for fodder, global production < 0.01 Mt) are set to 0 after the last old year. Gaps in the newdata (zero production) are filled by carrying the last available value forward.