SAN FRANCISCO — The value of semiconductor industry mergers and acquisitions declined for the fourth straight year in 2018 as the flood of high-value deals reached earlier in the decade continued to subside, according to the market research firm IC Insights.

Total chip industry deals reached in 2018 — including semiconductor companies, business units, product lines, and related assets — were worth roughly $23.2 billion last year, down from $28.1 billion in 2017, according to the firm’s estimates.

The value of industry acquisitions has fallen significantly since a peak of $107.3 billion in 2015. Still, the total value of M&A deals reached in the last year was almost twice the annual average during the first half of this decade, IC Insights said. Between 2010 and 2014, the value of chip industry deals averaged $12.6 billion per year, according to the firm.

The two largest acquisition agreements in 2018 — Microchip Technology’s $8.35 billion buy of Microsemi Corp. and Renesas Electronics’ $6.7 billion deal to acquire IDT — accounted for 65% of the industry’s total for the year.

Chip M&A value, IC Insights

Just two other semiconductor acquisitions announced in 2018 were worth more than $1 billion — Micron’s decision to excercise an option to take full ownership of its IM Flash joint venture with Intel for about $1.5 billion and Wingtech Technology’s moves to acquire Nexperia, a Dutch-based supplier of standard logic and discrete semiconductors that was spun out of NXP in 2017. According to IC Insights, Wingtech hopes to take majority ownership of Nexperia (about 76% of the shares) in 2019.

China’s refusal to approve the acquisition of NXP by Qualcomm — as well as other announced deals that fell through — resulted in the value of 2016 chip industry deals being adjusted downward from $100.4 billion to $59.3 billion, IC Insights said.