fluctuation in the world markets and on those that can be mined on a large scale and at low cost by strip mining or open pit methods, capital intensive with relatively low labor costs. For the most part these are located in countries that are enjoying relative political stability. The rapid rate of profit growth has been achieved by the combination of expanding existing properties while at the same time bringing new mines into production. Perhaps most significant of all has been the policy that we have pursued in selling the greater part of our output in advance under long-term sales contracts. In the last 10 years we have increased our mineral sales backlog from a lean $100 million to $2.45 billion at the end of last year and 77% of this backlog is represented by contracts containing escalation clauses protecting us against future cost increases and freezing in the profit margin. The existence of this backlog and the assurance that it affords us an income growth and increasing cash flow has given our stock an attractiveness not common to most other mining companies and at the same time allowed us to expand rapidly and finance that expansion largely with borrowed funds. Our mining gross revenues grew from $20. 7 million in 1966 to $83 million last year. We anticipate that in the next 5 years mining gross revenues will rise to $273 million, with $237 million represented by contractual commitments in hand and the remainder of $36 million derived from spot sales from uncommitted capacity being installed under our expansion program. Apart from the expansions being carried out and financed separately by Marcona and Pima, Utah's mining expansion program for the period 1968 to