In my case I also have to pay tax over the value of my entire wealth, and the way it works is that the value is calculated based on the total value on first of January. The higher the price of Bitcoin is on January the first, the more tax I end up paying. In that regard, it comes quite handy that Bitcoin always tends to crash in late December.
in january 2018 the price was over $10k and 2019 the price was under $5k so if your tax is based on value as of january each year. your at a loss. thus paying LESS tax this year