The Coinbase premium index, a key gauge of U.S. investor demand in the bitcoin market, has stayed positive for 14 straight days.

CoinDesk reported on April 22 that this is the longest bullish run since a period on Oct. last year when bitcoin traded above $126,000.

Based on data compiled by onchain analytics firm CoinGlass, the index did not turn negative even once from April 9 to 22. The Coinbase premium index shows whether bitcoin prices on Nasdaq-listed Coinbase are higher than on the global exchange Binance. Coinbase is seen as an exchange mainly used by U.S. institutional investors.

A positive reading indicates bitcoin is trading at a higher price on Coinbase than on Binance. When Coinbase shows a premium over Binance, it suggests U.S. buyers are aggressively buying bitcoin. The market views the index as a demand-confirmation signal because U.S. institutional funds, including regulated investment vehicles such as corporate treasuries, hedge funds and exchange-traded funds, use Coinbase as a key channel.

If the premium turns negative or shifts to a discount, it is interpreted as meaning U.S. demand is slowing and overseas markets are leading trading. The index stayed mostly in negative territory from mid-December last year to late February this year. Over the same period, bitcoin slid from about $100,000 to around $60,000.

The latest run of positive readings is drawing more attention because buying held up despite external setbacks. Demand persisted amid geopolitical noise and a DeFi crisis, and this is seen as a sign that U.S. funds continued to flow in even as the market was swayed by short-term news.

Prices also moved in step with the trend. Bitcoin climbed above $78,000 on April 22, and is up 14 percent this month.

The market is expected to focus on whether the premium extends further. Strong U.S. buying has repeatedly been a feature of bitcoin bull markets. If Coinbase maintains its price advantage again, it is expected to be a key gauge of whether U.S. institution-led demand can continue to support bitcoin's uptrend.