Feb 16 (Reuters) - The world's most valuable technology stocks have suffered sharp declines in market value this year after years of outsized gains, as investors question whether heavy spending on AI will generate sufficient returns to justify the lofty valuations.

Microsoft shares have fallen about 17% year-to-date on concerns over risks to its AI business and growing competition from Google's latest Gemini model and Anthropic's Claude Cowork AI agent, wiping roughly $613 billion off its market value to about $2.98 trillion as of Friday.

Amazon has shed around 13.85% so far this year, erasing about $343 billion in market value and leaving the company valued at roughly $2.13 trillion.

Earlier this month, Amazon said it expects capital spending to jump more than 50% this year.

Nvidia, Apple and Alphabet have also seen their market values decline by $89.67 billion, $256.44 billion and $87.96 billion, respectively, since the start of 2026, to $4.44 trillion, $3.76 trillion and $3.7 trillion.

The pullback signals a broader shift in market psychology, with investors moving from rewarding long-term AI ambitions to demanding near-term earnings visibility after years of speculative enthusiasm.

By contrast, TSMC, Samsung Electronics 005930.KS and Walmart have added $293.89 billion, $272.88 billion and $179.17 billion in market value, respectively, over the same period, lifting their valuations to $1.58 trillion, $817 billion and $1.07 trillion.