"A number of investors are looking at the future differential between interest rates and dividend yields."
Williamson said it was hard to see when the uptrend will end, but at some stage, investors will want to cash in some of their profits.
"This market is pretty hot at the moment. We've seen some pretty significant share price growth."
The NZX50's average dividend yield is 4.77 per cent, the third-highest across Asia-Pacific benchmark equity indices tracked by Refinitiv. The average price-to-earnings ratio is 18.59 times, the fifth highest.
The prospect of lower rates helped dent the kiwi dollar, which was trading below 68 US cents. A weaker currency is a boon for exporters, which reap bigger export receipts in New Zealand dollar terms.
Among those beneficiaries, Air New Zealand rose 2.7 per cent to $2.65, on a bigger volume than usual of 2.8 million shares. Fonterra Shareholders' Fund units were up 3 per cent at $4.44, Pushpay Holdings climbed 3.1 per cent to $3.35, A2 Milk increased 2 per cent to $14.58, and Fisher & Paykel Healthcare advanced 2.5 per cent to $15.98.
Kathmandu Holdings, which counts Australia as its biggest market, led the market higher, up 5.2 per cent at $2.41, on a volume of 159,000 shares, just below its 90-day average of 180,000.
Companies paying reliable dividends, such as utilities, have been in vogue among investors keen to replace fixed interest investments. Meridian Energy gave up some of those gains today, down 1.4 per cent at $4.14 on a volume of 1.5 million shares. A notice to the stock exchange showed director Mark Cairns bought 35,000 shares at an average price of $4.174 today.
Chorus also pared some of its recent gains, falling 0.4 per cent to $5.85 on a volume of 1.1 million shares. Genesis Energy slipped 0.5 per cent to $3.255 on 855,000, almost twice its three-month average.
Sky Network Television was the worst performer on the day, down 1.5 per cent at $1.32, with just 71,000 shares traded. Its 90-day average is 1.1 million.
Spark New Zealand was the most traded stock with 5.6 million shares changing hands. It fell 1.2 per cent to $3.775.
Of other stocks trading on volumes of more than a million, Kiwi Property Group rose 1 per cent to $1.51 after saying the value of its portfolio rose 1.5 per cent in the March quarter. Contact Energy was up 1.7 per cent at $7, Auckland International Airport rose 1.6 per cent to $8.35 and Z Energy gained 1.8 per cent at $6.39.
Outside the benchmark index, Plexure soared 35 per cent to 42 cents, the highest close in almost three years. Fast-food giant and Plexure customer McDonald's bought a 9.9 per cent stake in the NZX-listed firm for $5.4m, or 39 cents apiece. That was a premium to the 31 cents it closed at yesterday. The 1.9 million shares traded was more than 10 times its 90-day average.
Minnow biotech firm Blis Technologies rose 22 per cent, or 0.5 of a cent, to 2.8 cents, extending yesterday's 28 per cent gain when the firm said annual earnings beat expectations with strong orders in the March quarter.