A “favorite” Bitcoin (BTC) price signal could be about to turn bullish — and upside has always resulted, data shows.As noted by podcast host Preston Pysh on Oct. 18, the Long-Term & Short-Term Holder Realized Price Ratio (LTHSTH-RPR) looks primed to print a bull flag.Chart hints at return of the bullsIt may sound wordy, but LTHSTH-RPR is one of the most accurate Bitcoin price indicators. Its creator, Bitcoin 2021 conference organizer Dylan LeClair, confirmed his own bullishness based on its readings in late September.“TLDR: The lower the Short-Term:Long-Term Realized Price Ratio goes the more bullish I will become,” he wrote in an explanatory Twitter thread. “In the end, all bears will die.”Bitcoin LTHSTH-RPR chart. Source: Preston Pysh/ TwitterNow, with the indicator trending down for several months, it is high time for a rebirth — and BTC/USD has always benefited as a result.Under the hood, LTHSTH-RPR shows the cost basis of long-term holders and short-term holders. A long-term holder is defined by on-chain analytics firm Glassnode as an address holdings coins which have not moved in at least 155 days.“When the STH:LTH Realized Price Ratio is increasing, this means that STH cost basis is increasing relative to LTH cost basis, and vis versa,” LeClair added.“BTC rises when the marginal seller is exhausted. This is why you see the cost basis of LTHs stay stagnant during explosive bull runs, while the cost basis of STHs (many of whom are new market participants) explode – there are simply not enough coins to go around.”So far, LTH cost basis has not been eclipsed by STH cost basis — when this happens, the current downtrend should end.”Up only” remains the narrativeAs Cointelegraph reported, LTHSTH-RPR is just one of a number of BTC price metrics to have buoyed the bulls in recent weeks.Related: All-time high weekly close — 5 things to watch in Bitcoin this weekEverything from on-chain metrics to network fundamentals and even pure math suggests that further upside is imminent for Bitcoin — widely expected from Q4 of the year after a halving event.Nonetheless, analysts are already monitoring the market for an exit. The impact of this week’s exchange-traded fund (ETF) launches is also not anticipated to be a market mover in the short term.