Citi thinks it may be time to start buying stocks again, as its bear market model signals that conditions are improving. The bank's "bear market checklist," or BMC — which looks at a broad range of potential indicators for a market downturn, including valuation, credit spreads, M & A activity and fund flows — is currently raising six of 18 possible red flags. That's down from 8.5 flags at the end of last year. Robert Buckland, Citi's chief global equity strategist, noted that stocks have historically risen when the number of red flags comes down. "Buying when the BMC falls to the current 6/18 red flags has generated healthy 12-month gains (average +31%), even in multiyear bear markets," Buckland wrote in a note to clients Thursday. Some of the red flags that are still showing up on the checklist are return on equity, a flattish yield curve and high analyst bullishness. The S & P 500 has lost more than 16% so far this year, through Wednesday's close, and briefly dipped into an intraday bear market last week, as concerns over rising inflation and tighter monetary policy have led investors to dump riskier assets. The bear market model last flashed a buy-the-dip signal in February 2020 — at the onset of the Covid pandemic — when 5.5 of 18 flags were raised. The market bottomed in March 2020, then set off on a blistering rally that eventually carried it to record levels as recently as early January. "Even if the BMC does miss out on some factors, we would still expect an unsustainable global market peak to be accompanied by more than the 8.5/18 red flags experienced last December. In addition, we are reassured by the fall to 6/18 and the healthy 12m gains generated by buying at these levels in the past," Buckland said. "It is a brave call, but the BMC has made its name through making brave calls. It wants to buy this dip." Bottom line: The market has been under pressure for a host of reasons, including high inflation, rising interest rates, the war in Ukraine and Covid lockdowns in China. But if Citi's bear market checklist is correct, then market conditions have started to improve — and investors may want to start nibbling at stocks once again. — CNBC's Michael Bloom contributed reporting .