The tax burden of Americans was already among the lowest in the world, even before the tax cut that went into effect at the start of 2018.

But the cost of Social Security, Medicare and borrowing are likely to force the U.S. government to raise tax rates in the years ahead.

As a result, if you're nearing retirement or already retired, that makes this a good time to consider converting a traditional individual retirement account into a Roth IRA.