UPDATE 1-Casper Sleep shares pop 21% in market debut <!-- no image --> <div>Casper Sleep Inc's shares jumped 21% in their debut on Thursday, partially making up for the haircut the online mattress retailer took on its valuation after its offering was priced on Wednesday.<div class="feedflare"> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=_-gYaZYflQc:13xSnbd5wxQ:yIl2AUoC8zA"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?d=yIl2AUoC8zA" border="0"></a> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=_-gYaZYflQc:13xSnbd5wxQ:V_sGLiPBpWU"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?i=_-gYaZYflQc:13xSnbd5wxQ:V_sGLiPBpWU" border="0"></a> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=_-gYaZYflQc:13xSnbd5wxQ:F7zBnMyn0Lo"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?i=_-gYaZYflQc:13xSnbd5wxQ:F7zBnMyn0Lo" border="0"></a> </div><img src="http://feeds.feedburner.com/~r/reuters/UKBankingFinancial/~4/_-gYaZYflQc" height="1" width="1" alt=""></div> Posted by Reuters