We granted certiorari to review the decision of the court of appeals in Adolph Coors Co. v. Chames, 690 P.2d 893 (Colo.App.1984), which affirmed a district court judgment granting a tax refund on sales and use taxes paid from 1977 to 1980 by the Adolph Coors Company (Coors) on purchases of beer keg materials used in its beer-making business. The court of appeals held that the purchases were exempt from sales and use taxes because the beer kegs qualified as containers under sections 39-26-102(20)(a) and 39-26-203(1)(f)(I), 16B C.R.S. (1982). We affirm the judgment of the court of appeals.
I.
Coors, a Colorado corporation, brews and sells beer and has its principal place of business in Golden, Colorado. Coors paid Colorado sales taxes for the years 1978 to 1980 on certain materials (bung plates and tap wells), which were used in the assemblage of beer kegs, and paid Colorado use taxes for the years 1977 to 1979 on out-of-state purchases of other materials (aluminum discs), also used in manufacturing beer kegs.
On June 13, 1980, Coors filed a claim with the State of Colorado Department of Revenue (Department) for refunds in the total amount of $134,359.65 for sales and use taxes under section 39-26-102(20)(a), 16B C.R.S. (1982), and from use taxes under section 39-26-203(l)(f)(I), 16B C.R.S. (1982).
The essential facts are not in dispute. Coors is in the business of selling beer and cannot sell the beer without providing a container for it, such as a bottle, can, or keg. From 1977 to 1979, Coors purchased aluminum discs from Anaconda Corporation in St. Louis, Missouri, and paid the State of Colorado use taxes in the amounts of $15,699.65, $105,840.87, and $1,652.72 on these purchases. The discs were later transported by Coors to Hoover University, Inc. (Hoover), a corporation located in Beatrice, Nebraska, which manufactures beer kegs by forming the aluminum discs into keg halves and by welding the halves together and affixing a bung plate and a tap well to the keg. Hoover held a Colorado retail tax license. In the years 1978 to 1980, Coors paid Hoover for its labor in assembling the kegs and also paid Colorado sales taxes on the bung plates and tap wells in the amounts of $2,406.40, $6,676.61, and $2,083.10. The completed kegs were transported by Hoover to the Coors Brewery in Golden, Colorado.
From 1977 to 1980 Hoover manufactured 205,094 half-barrel kegs for Coors. The total cost for the completed half-barrel kegs, including the costs of the aluminum discs used in the manufacturing process, ranged from $44 per keg in 1977 to $54 per keg in 1980.1 Hoover also manufactured *13432,236 quarter-barrel kegs for Coors in 1979 at a cost of $39 each and 4,878 quarter-barrel kegs in 1980 at a cost of $40 each.
In its brewery, Coors fills the kegs with draft beer and delivers the kegs to its customers, mostly wholesale distributors, who then sell to retailers for resale to the ultimate consumers. The distributors are charged for the price of the beer plus a separate deposit of $12 for both the half- and quarter-barrel kegs. From 1977 to 1979 Coors charged distributors $9 for the beer in the quarter-barrel, and in 1980 it increased the price to $10. The price Coors charged distributors for the beer in a half-barrel keg was $15 in 1977 and $16 from 1978 to 1980. The charge for the beer plus the $12 deposit, therefore, varied from a low of $21 for a quarter-barrel keg in 1977 to a high of $28 for a half-barrel keg during the 1978-1980 period.
After the distributors purchase the beer from Coors, they in turn collect a $12 deposit per keg from the retailers, who then collect a $12 deposit from the consumer. When the empty kegs are returned by the consumers, the $12 deposit is refunded by the retailers, who then return the keg up the distribution line in exchange for the deposit. Coors places the deposits received from its distributors into a liability account until the keg is returned and the deposit is refunded to the distributor. The apparent purpose for requiring deposits is to cause the kegs to be returned to Coors for reuse.
Coors has a written agreement with its distributors that authorizes it to charge a distributor the full value of a keg if it is not returned, but Coors has never exercised that option or taken legal action against a distributor for failing to return a keg. However, during periods when there has been a shortage of kegs, Coors has urged its distributors to return the kegs more quickly. Coors washes and sterilizes the returned kegs for reuse, repairs them if necessary, and, if damaged beyond repair, sells them as scrap aluminum. The income from the scrap metal is recorded as miscellaneous income with any loss of value above the scrap metal value written off as a cost of doing business.
Coors’ deposit system has been successful, in that the majority of kegs are ultimately returned for reuse. The average half-barrel keg is reused from 59 to 71 times, and the average quarter-barrel keg is reused from 48 to 53 times.2 Coors inventories the kegs annually, including those in the hands of distributors and retailers. The number of kegs located during the inventory is subtracted from the number of kegs on Coors’ books, with the difference representing the number of kegs for which deposits have been forfeited. Coors declares forfeited deposits as miscellaneous income, not income from the sale of an asset, and continually purchases new kegs to replace those damaged beyond repair or not returned.3
*1344The Department made a final determination, pursuant to section 39-21-103(8), 16B C.R.S. (1982), that Coors was not entitled to a refund of the sales and use taxes. Coors appealed the final determination to the Jefferson County District Court, which reversed the determination and granted the refund on the basis that the beer kegs purchased by Coors were “containers” exempt from tax pursuant to section 39-26-102(20)(a), 16B C.R.S. (1982), and section 39-26-203(l)(f)(I)t 16B C.R.S. (1982).
The court of appeals affirmed the district cohrt, and we granted certiorari to consider whether Coors’ purchases of the beer keg materials qualify for the container exemptions under Colorado’s sales and use tax statutes.
The Department contends that the container exemptions should apply only to those containers which, along with the manufactured product, are resold by the manufacturer to its customers and should not exempt those containers that are owned and reused by the manufacturer. Coors, on the other hand, argues that all containers of a manufactured product are exempt regardless of their resale and, alternatively, that the beer kegs in question have been resold for the deposit charge within the meaning of the tax exemption statutes. For the reasons set forth in this opinion, we agree that Coors’ purchases of beer keg materials qualifies for the container exemptions.
II.
Colorado imposes a sales tax “[o]n the purchase price paid or charged upon all sales and purchases of tangible personal property at retail.” Section 39-26-104(1)(a), 16B C.R.S. (1982). Colorado also imposes a use tax on “the privilege of storing, using, or consuming in this state any articles of tangible personal property purchased at retail.” Section 39-26-202(1), 16B C.R.S. (1985 Supp.). The use tax is supplementary to the sales tax and does not apply to property subject to the sales tax. Section 39-26-203(1)(a), 16B C.R.S. (1982). As this court observed in Bedford v. Colorado Fuel and Iron Corp., 102 Colo. 538, 540, 81 P.2d 752, 753 (1938), the use tax “was designed to apply to the use and consumption of commodities elsewhere purchased at retail, which, if purchased in Colorado, would have been subject to the sales tax.” Because the sales and use taxing schemes are designed to complement each other, provisions of one should be interpreted in harmony with provisions of the other.
The exemptions at issue here are contained in sections 39 — 26—102(20)(a) and 39-26-203(l)(f)(I), 16B C.R.S. (1982). Pursuant to section 39-26-102(20)(a), the following transactions are exempt from the sales tax:
Sales to and purchases of tangible personal property by a person engaged in the business of manufacturing, compounding for sale, profit, or use, any article, substance, or commodity, which tangible personal property enters into the processing of or becomes an ingredient or component part of the product or service which is manufactured, compounded, or furnished, and the container, label, or the furnished shipping case thereof, shall be deemed to be wholesale sales and shall be exempt from taxation under this part 1.
(Emphasis added.)
Section 39-26-203(l)(f)(I) provides a similar exemption from the use tax:
(1) [The use tax] ... shall not apply:
(f)(1) To the storage, use, or consumption of tangible personal property by a person engaged in the business of manufacturing, compounding for sale, profit, or use, any article, substance, or commodity, which tangible personal property enters into the processing of or becomes an ingredient or component part of the product or service which is manufactured, compounded, or furnished, and the container, label, or the furnished shipping case.
(Emphasis added.)
This court previously construed these exemptions in Weed v. Occhiato, 175 Colo. *1345509, 488 P.2d 877 (1971). In Occhiato, we held that bottles purchased by a soft drink manufacturer and delivered by the manufacturer to buyers on a deposit and return basis were exempt containers pursuant to section 39-26-102(20)(a) and section 39-26-203(1)(f)(I). We rejected the Department’s argument that the word “container” did not include returnable bottles, and held:
We see nothing in the statutory provisions which suggest that non-returnable bottles are containers and returnable bottles are something else. Moreover, if the legislature had wished to make such a distinction, the manifestation of its intent could have been readily accomplished. To us, it appears elementary that a bottle is a container, and whether or not a bottle is returnable is clearly of no consequence....
If a change in the law is desired, it must be accomplished by the General Assembly, for neither the Director of Revenue nor this Court is empowered with taxing authority.
Id. at 511, 488 P.2d at 878-79 (emphasis added).
Occhiato is directly in point. We cannot say that a soft drink bottle is a container, and a beer keg is not a container. A beverage cannot be sold without a container. Just as the Department argued in Occhiato that the definition of “container” was restricted to non-returnable bottles, it now argues that the term is restricted to containers which are resold to the consumer. The Department attempts to distinguish Occhiato on the basis that returnable soft drink bottles, but not beer kegs, are resold to consumers, and that Occhiato is therefore consistent with its position that the container exemptions are limited to containers held for resale.
The Department’s argument, however, ignores the sound rationale of Occhiato. The phrase “container, label, or the furnished shipping case” contains no resale requirement, and we cannot restrict by judicial decision a provision that the General Assembly has left unrestricted. The Department urges us to follow the rule of construction that exemptions from tax must be construed against the taxpayer (citing United Presbyterian Association v. Board of County Commissioners, 167 Colo. 485, 496, 448 P.2d 967, 972 (1969)), while Coors relies on the rule that taxing acts must be construed in favor of the taxpayer (citing City of Denver v. Sweet, 138 Colo. 41, 52, 329 P.2d 441, 447 (1958)). In our view, it makes little difference whether the container exemptions are construed against or in favor of Coors; we cannot by construction amend the statute.
Significantly, the General Assembly amended the exemptions at issue here in 1982, yet it failed to alter our holding in Occhiato. See Ch. 153, sec. 1, § 39-26-102(20), 1982 Colo.Sess.Laws 568, 568; Ch. 153. sec. 3, § 39-26-203(1)(f), 1982 Colo. Sess.Laws 568, 569. Indeed, the container exemptions have remained unmodified and identical to their present form since they were originally enacted in 1935 and 1937. See Ch. 189, sec. 2(n), 1935 Colo.Sess.Laws 1000, 1003 (enacting the predecessor of section 39-26-102(20)(a), 16B C.R.S. (1982)); Ch. 230, art. VI. sec. 35(f), 1937 Colo.Sess. Laws 1098, 1100 (enacting the predecessor of section 39-26-203(1)(f)(I), 16B C.R.S. (1982)). It is well settled that an amendment of a statutory provision creates an inference of legislative approval of prior judicial interpretations left undisturbed by the amendment. See, e.g., Tompkins v. DeLeon, 197 Colo. 569, 571, 595 P.2d 242, 243-44 (1979) (“When the legislature reenacts or amends a statute and does not change a section previously interpreted by settled judicial construction, it is presumed that it agrees with judicial construction of the statute.”); Crownover v. Gleichman, 194 Colo. 48, 51, 574 P.2d 497, 499 (1977), cert. denied, 435 U.S. 905, 98 S.Ct. 1450, 55 L.Ed.2d 495 (1978) (“when a legislature repeatedly reenacts a statute which has theretofore received a settled judicial construction, ... it must be considered that the particular statute is reenacted with the understanding that there be adherence by the judiciary to its former construction”).
*1346Bedford v. Colorado Fuel and Iron Corp., 102 Colo. 538, 81 P.2d 752 (1938), and I.B.M. v. Charnes, 198 Colo. 374, 601 P.2d 622 (1979), relied on by the Department, are inapposite. In Bedford, we held that the purchase and use of mining equipment was subject to the sales and uses taxes where the equipment did not become a constituent part of a manufactured product held for sale. In I.B.M., we held that purchases of constituent parts later incorporated into office equipment were subject to the use tax if the office equipment was used by the manufacturer itself and not resold. In neither Bedford nor I.B.M. did we discuss or interpret the container exemptions at issue here.
Courts of other jurisdictions interpreting similar provisions are in accord with the result we reach today. See, e.g., Undercofler v. Buck, 107 Ga.App. 870, 132 S.E.2d 157 (1963) (the sale and use of returnable milk and soft drink bottles are exempt from tax pursuant to exemption for “containers, labels, sacks, or bags used for packaging tangible personal property for shipment or sale”); Coca-Cola Bottling Plants, Inc. v. Johnson, 147 Me. 327, 87 A.2d 667 (1952) (distinction between returnable and non-returnable containers unimportant in construction of provision exempting “[containers] sold to persons for use in packing, packaging or shipping tangible personal property produced or sold by them”); Evans v. Memphis Dairy Exchange, 194 Tenn. 317, 250 S.W.2d 547 (1952) (court will not imply a resale requirement in statute exempting from tax “containers ... used for packaging tangible personal property for shipment or sale”). But see Gay v. Canada Dry Bottle Co. of Florida, 59 So.2d 788 (Fla.1952) (exemption for “containers ... [which are intended to be used one time only and are] used for packaging tangible personal property for shipment or sale” does not apply to containers sold on a deposit and return basis).
Accordingly, we must conclude that the only relevant inquiry in applying the container exemptions is whether the materials purchased by Coors were later used as “containers” in the sale of manufactured goods. Once stated in these terms, it cannot be disputed that Coors’ purchases of beer keg materials qualifies for the exemptions.
III.
Even assuming that the container exemptions require “resale,” we hold that the beer kegs were “resold” when delivered by Coors to beer purchasers in exchange for a deposit refundable upon return of the beer keg.
The definition of a “sale” in the Colorado sales tax act is of little help in determining whether a delivery of a container on a deposit and return basis is a “resale” of the container. Section 39-26-102(10), 16B C.R.S. (1982), provides:
“Sale” or “sale and purchase” includes installment and credit sales and the exchange of property as well as the sale thereof for money; [and] every such transaction, conditional or otherwise, for a consideration, constituting a sale;....
Courts in other jurisdictions, however, have declared that delivery of a container on a deposit and return basis is a “resale” for purposes of sales and use taxation. See, e.g., Belleville Dr. Pepper v. Korshak, 36 Ill.2d 352, 221 N.E.2d 635 (1966) (purchase of bottles and cases by a soft drink manufacturer was a nontaxable, wholesale transaction because delivery of the bottles and cases to soft-drink buyers for a refundable deposit of forty percent of the actual cost of the bottles was a “resale”); Department of Treasury v. Fairmount Glass Works, 113 Ind.App. 684, 49 N.E.2d 1 (1943) (purchase of bottles by a brewer was a wholesale transaction because “sale or return” delivery of the bottles to beer purchasers was a “resale”); Coca-Cola Bottling Works Co. v. Kentucky Department of Revenue, 517 S.W.2d 746 (Ky.1974) (purchase of bottles and cases by a soft-drink manufacturer was a nontaxable, wholesale transaction because delivery of the bottles to soft-drink buyers for a refundable, two-cent per bottle deposit was a “resale”); Goebel Brewing Co. v. Brown, 306 Mich. *1347222, 10 N.W.2d 835 (1943) (purchase of bottles and cartons by a brewer was a nontaxable, wholesale transaction because delivery of the bottles and cartons to beer buyers for a refundable deposit was a “resale”).
In addition, the Colorado Uniform Commercial Code indicates that deposit-and-return containers are “resold” when delivered to product buyers. Section 4-2-106(1), 2 C.R.S. (1973), provides that “[a] ‘sale’ consists in the passing of title from the seller to the buyer for a price.... ” “Price” is not defined in the Code, but “value” includes “any consideration sufficient to support a simple contract.” § 4-1-201(44)(d), 2 C.R.S. (1973). It is axiomatic contract law that legal sufficiency of consideration does not depend on the comparative economic value of the exchange and that consideration is not insufficient merely because it is inadequate. Restatement (Second) of Contracts § 79 (1981); Lampley v. Celebrity Homes, Inc., 42 Colo.App. 359, 594 P.2d 605 (1979). The small price of the deposit for the beer kegs, by itself, clearly cannot preclude a finding of “resale.”
Finally, section 4-2-401(l)-(2), 2 C.R.S. (1973), discusses “passing of title”:
Any retention or reservation by the seller of the title (property) in goods shipped or delivered to the buyer is limited in effect to a reservation of a security interest. ...
(2) Unless otherwise explicitly agreed, title passes to the buyer at the time and place at which the seller completes his performance with reference to the physical delivery of the goods, despite any reservation of a security interest and even though a document of title is to be delivered at a different time or place....
There is no question that Coors delivered the beer kegs to the buyers. Under the quoted statutory language, any contractual arrangements used by Coors to “reserve title” in order to ensure return of the kegs could not stop title from passing and thereby prevent a “sale.” The provision in the sales contracts requiring return of the kegs could create, at most, a security interest in favor of Coors. The kegs therefore were “resold” when delivered to beer purchasers in exchange for a refundable deposit, and Coors’ purchases of materials to construct the kegs are exempt from sales and use taxation even under the department’s restrictive interpretation.
The judgment of the court of appeals is affirmed.
QUINN, C.J., dissents. DUBOFSKY and LOHR, JJ., join in the dissent.. From 1977 to 1980, Coors paid Hoover for the half-barrel kegs at the price per keg and for the number of kegs listed below:
*134351,005 100,963 $44/each 48/each t— CO c- c~ © ©
34,476 49/each © c- ©
18,650 54/each ® 00 ©
. For the years 1978-1980 Coors sold keg beer in the following amounts:
1/2 Barrel Kegs 1/4 Barrel Kegs
1978 2,316,993 147,834
1979 2,418,048 157,841
1980 2,694,151 176,806
The number of beer kegs in the possession of Coors and its distributors, based on its annual inventories, were:
1/2 Barrel Kegs 1/4 Barrel Kegs
1978 370,764 29,127
1979 388,132 30,868
1980 358,799 31,529
The number of times the average keg is used per year can be calculated by taking the number of sales in each year divided by the number of kegs in inventory for the same year. This calculation yields the following annual uses per keg:
1/4 Barrel Kegs bfi g ⅛
rH rH ⅞0 1ÓIÍ5U5 <N <N! tq t-00 05 © © ⅜ ©
Each keg has a useful life of nine and one-half years, with the result that each half-barrel keg will be used approximately 59-71 times (6.2 x 9.5 = 59, 7.5 x 9.5 = 71) and each quarter-barrel keg will be used 48-53 times (5.1 x 9.5 = 48, 5.6 x 9.5 = 53).
. In 1980, Coors declared $1,134,000 in income from forfeited deposits.