Not only is cash a very different payment instrument than checks, but consumers choose to use cash more frequently than any other payment instrument, including debit or credit cards. Cash plays a dominant role for small-value transactions, is the leading payment instrument for many types of purchases, and stands as the key alternative when other options are not available. In certain cases, including that of mostly lower-income consumers who lack access to alternative payment options or find them too costly or difficult to obtain, cash is also used for relatively larger-value transactions. Using the DCPC data, this paper explores where, how, and why people use the various payment options and highlights the key and enduring roles cash continues to play in consumer transactions.  

http://www.frbsf.org/cash/publications/fed-notes/2014/april/cash-consumer-spending-payment-diary