Stocks closed near the flatline on Thursday as market participant digested December's hotter-than-expected consumer price index reading. The Dow Jones Industrial Average added about 15 points, while the S&P 500 Index ticked slightly lower and the Nasdaq Composite closed at a positive flatline.

Here's how the market settled on Thursday:

S&P 500 Index (SPY  ): -0.07% or -3.21 points to 4,780.24

Dow Jones Industrial Average (DIA  ): +0.04% or +15.29 points to 37,711.02

Nasdaq Composite Index (QQQ  ): +0.00% or +0.54 points to 14,970.18

Making headlines, the consumer price index (CPI) rose 0.3% on the month and 3.4% on a 12-month basis in December, the Labor Department reported Thursday, coming in slightly above expectations as inflation remains above the Federal Reserve's 2% target. Still, inflation has eased throughout 2023, with annual CPI coming in at 6.4% in December 2022.

Beneath the headline, core CPI -- which excludes volatile food and energy prices -- rose 0.3% on the month and 3.9% year-over-year, coming roughly in-line with estimates and marking the lowest annual core reading since May 2021.

Also in the news, Coinbase (COIN  ) and Robinhood (HOOD  ) shares came under pressure as market participants weighed the potential impacts of newly minted Bitcoin exchange-traded funds could have on the crypto trading platforms. This comes as a host of new Bitcoin ETFs began trading on Thursday after the U.S. Securities and Exchange Commission (SEC) approved rule changes for the funds on Wednesday.

"We see the impact of a Bitcoin ETF as having both positive and risky elements for Coinbase, but given the appreciation of Coinbase's stock price, we see the risks as more relevant to shareholders," JPMorgan analyst Kenneth Worthington wrote in a Thursday note.

In single-stock news, Boeing (BA  ) was in the spotlight again on Thursday after the Federal Aviation Administration announced it has opened a probe into the aerospace manufacturer in response to the Alaska Airlines (ALK  ) flight incident where a panel on its Boeing 737 Max 9 plans blew off mid-flight over the weekend.

The investigation will access whether Boeing "failed to ensure completed products conformed to its approved design and were in a condition for safe operation in compliance with FAA regulation," the federal agency said in a statement.

Citigroup (C  ) warned investors late Wednesday that its fourth-quarter results were impacted by $880 million in currency conversion losses from the decline of the Argentine peso and $780 million in restructuring costs. The bank is set to deliver its earnings results Friday morning.

Looking ahead, traders will react to the start of the fourth-quarter earnings season, with big banks including Bank of America (BAC  ), JPMorgan Chase (JPM  ) and Wells Fargo (WFC  ) set to report results Friday morning.