The chart shows the historic gold/silver ratio from 1980. The ratio was 16 in 1980. The dotted line shows the median level of about 62, which at $1500 gold would mean $24 silver. A ratio of 16 would mean $93 silver.
Silver seems unlikely to return to the historic 16 to 1 ratio now that governments are no longer drawing supply for minting silver coins intended for everyday use as money.
Long term holders can use this chart to make allocation decisions on purchasing and selling gold or silver.
March 18 update: The ratio today had a high of 131.41 which is a 5000 year record.