The US Federal Reserve has increased interest rates for only the third time since the 2007-2009 recession, but how big a deal this is depends on what happens next.
Sometimes, two or three years after the US Federal Reserve begins a period of increasing interest rates trouble sets in.
We saw it happen in the last decade, we saw it happen in the decade before. During the mid 1990s, US interest rates rose, leading to a reversal of money flows between the US and emerging markets. When US rates were low, investors poured money into emerging markets, especially the so called tiger economies of south east Asia, but when US rates went up, the money left, returned to the US, exposing nasty weaknesses in the region. Then in 1997 we saw the Asian crisis, the following year the Russian crisis. At the time this was a big deal, and for the regions affected the end result was a very deep economic depression.
During the first decade of this century, US rates rose, but this time the problem that was exposed stood much closer to home. The US subprime crisis happened. We saw the worst economic recession in the West in 80 years.
Now US rates are going up again. They rose at the end of 2015, again at the end of 2016, and then again today - 15th March 2017.
Markets expect two more hikes this year.
Will it end in tears again?
Emerging markets have managed to run-up big debts again, China especially, but in most cases, this time around there is less reliance on foreign debt - Turkey being one of the main exceptions to this.
Household debt has rocketed in several western economies, and house prices look frothy in some - Sweden and Australia, in particular.
As for US household debt, it is getting worryingly high, but maybe is not quite at a level that could induce a crisis.
What matters is what happens next.
Today also saw the latest figures on US inflation, the headline rate rose to 2.7 per cent, a five year high, but core inflation, that's minus food and energy, is at a more modest 2.2 per cent. US core inflation has sat within a corridor of between 2.0 and 2.3 per cent for 15 months now. So, no cause for alarm emanating from the latest inflation data.
Markets expect two more rate hikes this year, and for US rates to hit two per cent by the end of next year. And if this happens, history may not repeat itself; crisis probably won't follow.
But, if US inflation rises faster than expected, maybe in part down to President Trump's economic policies, and if lighter financial regulation in the US pushes household debt levels much higher, things may go pear shaped, eventually.