The only reliable way to evaluate forecasting accuracy is track record. Four references are given below.
The first one. On February 16, 2019 Airbus decided to discontinue the production of the A380 after having sold barely 400 units. The page below is from my book Conquering Uncertainty published in 1998. The highlighted forecast was made with data up to 1996!
Forecast on A380
The second concerns stock-market forecasts as described in An S-Shaped Trail to Wall Street.
ETFs for Oil, Gold, Dollar, and others
The third results from the iPad/iPhone application Stocks' Futures.
The Wal-Mart Stock Price
The fourth one is one of many cases treated in the book An S-Shaped Adventure - PREDICTIONS 20 Years Later.
The World Energy Consumption