01/09/2012 03:56 EST | Updated 03/10/2012 05:12 EST

Apple shares hit all-time high

Shares of Apple Inc. closed down Monday after reaching an all-time high earlier in the day as a major investment bank increased its earnings projections for the technology giant.

Its stock ended at $421.73 US, down 67 cents, after rising as high as $427.75.

John Pliniussen, a business professor at Queen’s University in Kingston, Ont., said the strength of the share price shows Apple is still going strong in the wake of the death of its co-founder in October.

"Apple is so strong and the product development and marketing team Steve Jobs amassed hasn’t slowed down, even after his death," said Pliniussen. "The momentum Steve Jobs started is continuing today."

Apple reached its previous 52-week high in mid-October, only to lose almost seven per cent over the next five trading days.

The stock rose after investment bank Goldman Sachs raised its estimate of the earnings Apple will report later this month for the three months ending in December and raised its projections for iPhone sales.

Those increased sales could come at the expense of Waterloo, Ont.-based Research in Motion. RIM's shares, which have gained recently amid speculation of a management shakeup or takeover offer, rose 12 cents to 15.90 in Toronto.