The only reliable way to evaluate forecasting accuracy is track record. Three references are given below.
The first one concerns stock-market forecasts as described in An S-Shaped Trail to Wall Street.
ETFs for Oil, Gold, Dollar, and others
The second results from the iPad/iPhone application Stocks' Futures.
The Wal-Mart Stock Price
The third one is one of many cases treated in the book An S-Shaped Adventure - PREDICTIONS 20 Years Later.
The World Energy Consumption