He has been looking at the correlation between the benchmark for US stocks, the S&P 500 Index, and riskier currencies such as the kiwi and the Aussie.
"It's been much closer in the last month than it has been for many, many years," Speizer said.
"If you're wanting to know what the currency is going to do in this environment, it will do whatever the S&P 500 is doing, but to a lesser extent."
Currency markets of late have been less volatile than other asset classes, such as interest rates and commodities.
The S&P 500 Index eased 0.2 per cent overnight New Zealand time, despite having been in positive territory for much of the trading session. Currently, the futures are barely positive.
The latest coronavirus statistics show the US now has more than 400,000 people infected by the Covid-19 virus and deaths there are approaching 13,000. Not all infections or deaths are being counted because of a lack of testing.
In New Zealand, the number new probable and confirmed cases today was just 50, down from 89 on April 2 and April 5, suggesting the nation's lockdown, which will reach two weeks at midnight, has slowed the spread of Covid-19. The nation has recorded just a single death.
The New Zealand dollar was trading at 97.10 Australian cents from 97.27 cents at 5pm yesterday. It was at 48.35 British pence from 48.71, at 54.81 euro cents from 55.25, at 64.87 yen from 65.07 and at 4.2081 Chinese yuan from 4.2327.
The bid price on the two-year swap rate closed at 0.4775 per cent from 0.4700 yesterday, while 10-year swaps were at 1.0450 per cent from 0.9850.
