MYL chart thread, page-207

SVL is much more leveraged to silver price.
to illustrate the example crudely, if 100% of their resource is silver, and 33% of MYL's resource is silver by value, you'd expect their share price to have 3x more volatility driven by changes in the silver price.

silver price increased by roughly 40c/oz over the same period you're referring to.

If all you want is silver exposure because you think silver is going to $50/oz head over to SVL. Mineral diversification makes MYL much lower risk (in terms of metals price) and incidentally far less volatile.