20.
Operating leases We lease certain property, computer and communications equipment, transportation equipment and other equipment through operating leases.
Total rental expense for operating leases was $331 million, $375 million and $371 million for 2017, 2016 and 2015, respectively.
Minimum payments for operating leases having initial or remaining non-cancelable terms in excess of one year are:
## Table 0 ##
21.
Guarantees and product warranty Caterpillar dealer performance guarantees We have provided an indemnity to a third-party insurance company for potential losses related to performance bonds issued on behalf of Caterpillar dealers.
The bonds have varying terms and are issued to insure governmental agencies against nonperformance by certain dealers.
We also provided guarantees to third-parties related to the performance of contractual obligations by certain Caterpillar dealers.
These guarantees have varying terms and cover potential financial losses incurred by the third-parties resulting from the dealers’ nonperformance.
In 2016, we provided a guarantee to an end user related to the performance of contractual obligations by a Caterpillar dealer.
Under the guarantee, which expires in 2025, non-performance by the Caterpillar dealer could require Caterpillar to satisfy the contractual obligations by providing goods, services or financial compensation to the end user up to an annual designated cap.
Customer loan guarantees We provide loan guarantees to third-party lenders for financing associated with machinery purchased by customers.
These guarantees have varying terms and are secured by the machinery.
In addition, Cat Financial participates in standby letters of credit issued to third parties on behalf of their customers.
These standby letters of credit have varying terms and beneficiaries and are secured by customer assets.
Supplier consortium performance guarantees We have provided guarantees to a customer in Brazil and a customer in Europe related to the performance of contractual obligations by supplier consortiums to which our Caterpillar subsidiaries are members.
The guarantees cover potential damages incurred by the customers resulting from the supplier consortiums’ nonperformance.
The damages are capped except for failure of the consortiums to meet certain obligations outlined in the contract in the normal course of business.
The guarantees will expire when the supplier consortiums perform all their contractual obligations, which are expected to be completed in 2022 for the customer in Europe and 2025 for the customer in Brazil.
Third party logistics business lease guarantees We have provided guarantees to third-party lessors for certain properties leased by a third party logistics business, formerly Caterpillar Logistics Services LCC, in which we sold our equity interest in 2015.
The guarantees are for the possibility that the third party logistics business would default on real estate lease payments.
The guarantees were granted at lease inception and generally will expire at the end of the lease terms.
We have dealer performance guarantees and third party performance guarantees that do not limit potential payment to end users related to indemnities and other commercial contractual obligations.
In addition, we have entered into contracts involving industry standard indemnifications that do not limit potential payment.
For these unlimited guarantees, we are unable to estimate a maximum potential amount of future payments that could result from claims made.
No significant loss has been experienced or is anticipated under any of these guarantees.
At both December 31, 2017 and 2016, the related liability was $8 million.
The maximum potential amount of future payments (undiscounted and without reduction for any amounts that may possibly be recovered under recourse or collateralized provisions) we could be required to make under the guarantees at December 31 are as follows:
## Table 1 ##
Cat Financial provides guarantees to repurchase certain loans of Caterpillar dealers from a special-purpose corporation (SPC) that qualifies as a variable interest entity.
The purpose of the SPC is to provide short-term working capital loans to Caterpillar dealers.
This SPC issues commercial paper and uses the proceeds to fund its loan program.
Cat Financial has a loan purchase agreement with the SPC that obligates Cat Financial to purchase certain loans that are not paid at maturity.
Cat Financial receives a fee for providing this guarantee, which provides a source of liquidity for the SPC.
Cat Financial is the primary beneficiary of the SPC as its guarantees result in Cat Financial having both the power to direct the activities that most significantly impact the SPC’s economic performance and the obligation to absorb losses, and therefore Cat Financial has consolidated the financial statements of the SPC.
As of December 31, 2017 and 2016, the SPC’s assets of $1,107 million
ÿþReconciliations of adjusted profit before taxes to the most directly   comparable GAAP measure, consolidated profit (loss) before taxes,   are as follows:  @T@  Reconciliations of adjusted profit per share to the most directly   comparable GAAP measure, diluted profit per share, are as follows:  @T@  Reconciliations of adjusted profit per share to the most directly   comparable GAAP measure, diluted profit per share, are as follows:  @T@  1 At statutory tax rates prior to consideration of U.
S.
 tax reform.
 Full year 2017   also includes $15 million increase to prior year taxes related to non-U.
S.
   restructuring costs.
  2   At statutory tax rates prior to consideration of U.
S.
 tax reform.
  3   Net of U.
S.
 federal tax at 35 percent.
  4   Includes a $17 million tax benefit.
  Per share amounts computed using fully diluted shares outstanding except for   consolidated loss per share, which was computed using basic shares outstanding.
  Supplemental Consolidating Data  We are providing supplemental consolidating data for the purpose of   additional analysis.
 The data has been grouped as follows:  Consolidated   Caterpillar Inc.
 and its subsidiaries.
  Machinery, Energy & Transportation   Caterpillar defines   Machinery, Energy & Transportation as it is presented in the   supplemental data as Caterpillar  Inc.
 and its subsidiaries with   Financial Products accounted for on the equity basis.
 Machinery,   Energy & Transportation information relates to the design,   manufacturing and marketing of our products.
 Financial Products    information relates to the financing to customers and dealers for the   purchase and lease of Caterpillar and other equipment.
 The nature   of these businesses is different, especially with regard to the financial   position and cash flow items.
 Caterpillar management utilizes this   presentation internally to highlight these differences.
 We also believe   this presentation will assist readers in understanding our business.
  Financial Products   Our finance and insurance subsidiaries,   primarily Cat Financial and Insurance Services.
  Consolidating Adjustments   Eliminations of transactions between   Machinery, Energy & Transportation and Financial Products.
  Pages 68 to 70 reconcile Machinery, Energy & Transportation with   Financial Products on the equity basis to Caterpillar Inc.
 consolidated   financial information.

## Table 2 ##
## Table 3 ##
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS 1.
Operations and summary of significant accounting policies A.
Nature of operations Information in our financial statements and related commentary are presented in the following categories: Machinery, Energy & Transportation (ME&T) – Represents the aggregate total of Construction Industries, Resource Industries, Energy & Transportation and All Other operating segments and related corporate items and eliminations.
Financial Products – Primarily includes the company’s Financial Products Segment.
This category includes Caterpillar Financial Services Corporation (Cat Financial), Caterpillar Insurance Holdings Inc.  (Insurance Services) and their respective subsidiaries.
Our products are sold primarily under the brands “Caterpillar,” “CAT,” design versions of “CAT” and “Caterpillar,” “EMD,” “FG Wilson,” “MaK,” “MWM,” “Perkins,” “Progress Rail,” “SEM” and “Solar Turbines”.
We conduct operations in our Machinery, Energy & Transportation lines of business under highly competitive conditions, including intense price competition.
We place great emphasis on the high quality and performance of our products and our dealers’ service support.
Although no one competitor is believed to produce all of the same types of equipment that we do, there are numerous companies, large and small, which compete with us in the sale of each of our products.
Our machines are distributed principally through a worldwide organization of dealers (dealer network), 48 located in the United States and 123 located outside the United States, serving 192 countries.
Reciprocating engines are sold principally through the dealer network and to other manufacturers for use in products.
Some of the reciprocating engines manufactured by our subsidiary Perkins Engines Company Limited, are also sold through its worldwide network of 93 distributors covering 182 countries.
The FG Wilson branded electric power generation systems primarily manufactured by our subsidiary Caterpillar Northern Ireland Limited are sold through its worldwide network of 154 distributors covering 131 countries.
Some of the large, medium speed reciprocating engines are also sold?
under the MaK brand through a worldwide network of 20 distributors covering 130 countries.
Our dealers do not deal exclusively with our products; however, in most cases sales and servicing of our products are the dealers’ principal business.
Some products, primarily turbines and locomotives, are sold directly to end customers through sales forces employed by the company.
At times, these employees are assisted by independent sales representatives.
The Financial Products line of business also conducts operations under highly competitive conditions.
Financing for users of Caterpillar products is available through a variety of competitive sources, principally commercial banks and finance and leasing companies.
We offer various financing plans designed to increase the opportunity for sales of our products and generate financing income for our company.
A significant portion of Financial Products activity is conducted in North America, with additional offices in Latin America, Asia/Pacific, Europe, Africa and Middle East.
B.
Basis of presentation The consolidated financial statements include the accounts of Caterpillar?
Inc.  and its subsidiaries where we have a controlling financial interest.
Investments in companies where our ownership exceeds 20 percent and we do not have a controlling interest or where the ownership is less than 20 percent and for which we have a significant influence are accounted for by the equity method.
See Note 9 for further discussion.
We consolidate all variable interest entities (VIEs) where Caterpillar Inc.  is the primary beneficiary.
For VIEs, we assess whether we are the primary beneficiary as prescribed by the accounting guidance on the consolidation of VIEs.
The primary beneficiary of a VIE is the party that has both the power to direct the activities that most significantly impact the entity’s economic performance and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE.
See Note 21 for further discussion on a consolidated VIE.
We have affiliates, suppliers and dealers that are VIEs of which we are not the primary beneficiary.
Although we have provided financial support, we do not have the power to direct the activities that most significantly impact the economic performance of each entity.
Our maximum exposure to loss from VIEs for which we are not the primary beneficiary was as follows:

<table><tr><td>2018</td><td>2019</td><td>2020</td><td>2021</td><td>2022</td><td>Thereafter</td><td>Total</td></tr><tr><td>$211</td><td>$142</td><td>$104</td><td>$74</td><td>$58</td><td>$169</td><td>$758</td></tr></table>
<table><tr><td>(Millions of dollars)</td><td>2017</td><td>2016</td></tr><tr><td>Caterpillar dealer performance guarantees</td><td>$1,313</td><td>$1,384</td></tr><tr><td>Customer loan guarantees</td><td>40</td><td>51</td></tr><tr><td>Supplier consortium performance guarantees</td><td>565</td><td>278</td></tr><tr><td>Third party logistics business lease guarantees</td><td>69</td><td>87</td></tr><tr><td>Other guarantees</td><td>118</td><td>56</td></tr><tr><td>Total guarantees</td><td>$2,105</td><td>$1,856</td></tr></table>
<table><tr><td></td><td colspan="2">Three Months Ended December 31,</td><td colspan="2">Twelve Months Ended December 31,</td></tr><tr><td>(millions of dollars)</td><td>2017</td><td>2016</td><td>2017</td><td>2016</td></tr><tr><td>Profit (Loss) before taxes</td><td>$1,111</td><td>$-1,348</td><td>$4,082</td><td>$139</td></tr><tr><td>Restructuring costs</td><td>$245</td><td>$395</td><td>$1,256</td><td>$1,019</td></tr><tr><td>Mark-to-market losses</td><td>$301</td><td>$985</td><td>$301</td><td>$985</td></tr><tr><td>Gain on sale of equity investment</td><td>$—</td><td>$—</td><td>$-85</td><td>$—</td></tr><tr><td>Goodwill impairment</td><td>$—</td><td>$595</td><td>$—</td><td>$595</td></tr><tr><td>Adjusted profit before taxes</td><td>$1,657</td><td>$627</td><td>$5,554</td><td>$2,738</td></tr></table>
<table><tr><td></td><td colspan="2">Three Months Ended December 31,</td><td colspan="2">Twelve Months Ended December 31,</td></tr><tr><td></td><td>2017</td><td>2016</td><td>2017</td><td>2016</td></tr><tr><td>Profit (Loss) per share - diluted</td><td>$-2.18</td><td>$-2.00</td><td>$1.26</td><td>$-0.11</td></tr><tr><td>Per share restructuring costs<sup>1</sup></td><td>$0.31</td><td>$0.45</td><td>$1.68</td><td>$1.16</td></tr><tr><td>Per share mark-to-market losses<sup>2</sup></td><td>$0.26</td><td>$1.14</td><td>$0.26</td><td>$1.15</td></tr><tr><td>Per share state deferred tax valuation allowance (reversal)<sup>3</sup></td><td>$-0.18</td><td>$0.24</td><td>$-0.18</td><td>$0.24</td></tr><tr><td>Per share gain on sale of equity investment<sup>2</sup></td><td>$—</td><td>$—</td><td>$-0.09</td><td>$—</td></tr><tr><td>Per share U.S. tax reform impact</td><td>$3.91</td><td>$—</td><td>$3.95</td><td>$—</td></tr><tr><td>Per share goodwill impairment<sup>4</sup></td><td>$—</td><td>$0.98</td><td>$—</td><td>$0.98</td></tr><tr><td>Adjusted profit per share</td><td>$2.16</td><td>$0.83</td><td>$6.88</td><td>$3.42</td></tr><tr><td colspan="5"><sup>1</sup>At statutory tax rates prior to consideration of U.S. tax reform. Full year 2017 also includes $15 million increase to prior year taxes related to non-U.S. restructuring costs.</td></tr><tr><td><sup>2</sup>At statutory tax rates prior to consideration of U.S. tax reform.</td><td></td><td></td><td></td><td></td></tr><tr><td><sup>3</sup>Net of U.S. federal tax at 35 percent.</td><td></td><td></td><td></td><td></td></tr><tr><td><sup>4</sup>Includes a $17 million tax benefit.</td><td></td><td></td><td></td><td></td></tr><tr><td colspan="5">Per share amounts computed using fully diluted shares outstanding except for consolidated loss per share, which was computed using basic shares outstanding.</td></tr></table>

Question: Which year / section is Per share mark-to-market losses in Twelve Months Ended December 31 the lowest?
Answer: 2017