Deagel's population and economic forecasts from 2017 to 2025 has been mentioned several times in this thread.
Here is their complete list for all countries - https://nobulart.com/wordpress/wp-co...by-Country.pdf
Britain tops the list for the highest population decline (-77.1%), followed by Ireland (-72.4%) and the USA (-68.5%). Unsurprisingly, those countries suffer the greatest drop in GDP.