Supermarket Income REIT (SUPR) 77.1p Market cap: £959 million Experts reckon we could survive three days or nine meals with empty supermarket shelves before a full-blown societal collapse. That's how vital supermarkets are to our everyday existence. So, invest in shares of Tesco (TSCO), Sainsbury's (SBRY) or Marks & Spencer (MKS) during times of market turbulence? That is a possible option,...