Review of DotEcon’s Recommendations
Peter Cramton and Pacharasut Sujarittanonta 1
15 July 2019

The Dutch government intends to hold a spectrum auction of the 700 MHz, 1400 MHz, and 2100 MHz
frequency bands at the end of 2019 or early 2020. The Ministry of Economic Affairs has asked DotEcon to
make a recommendation about the appropriate auction model and rules. We were asked by the Ministry
to provide independent peer review of DotEcon’s advice. This report comments on DotEcon’s
recommendations, “Recommended auction model for the award of 700, 1400 and 2100 MHz spectrum”.

Peter Cramton is a Professor of Economics at the University of Cologne and the University of Maryland; his research
focuses on market design; he has applied that research to design auction-based markets of radio spectrum,
electricity, financial securities, and other products. Pat Sujarittanonta is on the Faculty of Economics at
Chulalongkorn University in Thailand and a Principal of Cramton Associates LLC; he has extensive experience in
spectrum auctions, wholesale electricity markets and antitrust issues.
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1 Introduction
We have been asked by the Dutch Ministry of Economic Affairs and Climate Policy (henceforth the
Ministry) to provide independent peer review of DotEcon’s draft recommendations on the spectrum
auction of 700 MHz, 1400 MHz, and 2100 MHz frequency bands (henceforth Dutch multiband auction).
This report evaluates DotEcon’s draft recommended auction model for the award of 700, 1400, and 2100
MHz spectrum 2.
This report is prepared with the following objectives in mind:
1) To assess whether DotEcon’s draft recommended auction model is the result of careful
consideration of the relevant factors that go into an advice on the choice of auction format.
2) To assess whether DotEcon’s draft recommended auction model is sufficiently motivated.
As part of this task, we have reviewed the inputs and thoroughly evaluated DotEcon’s recommended
auction model considering the Ministry’s auction objectives.

2 Ministry objectives and key assumptions
The Ministry laid out the auction objectives as follows.
The auction should produce an efficient allocation of the available spectrum. This will
firstly require making sure that all potential participants to the auction have a realistic
chance of winning, and secondly, that the auction produces a realistic revenue. Any
strategic bidding behavior, for example with the intent to keep out new entrants or
thwart competitors, will prevent an efficient allocation from emerging and the auction
design should not incentivize or facilitate this behavior. Within this overarching
objective of an efficient allocation the Ministry’s goals for the auction are, in order,
simplicity, transparency, and freedom of choice.
We evaluate the recommended auction model and alternatives in light of these objectives, recognizing
the specific setting of the auction. The primary objective is putting the spectrum to its best use—an
efficient allocation of the spectrum. Secondary objectives, in order, are realistic revenues, simplicity,
transparency, and freedom of choice.
Following the merger of T-Mobile and Tele2, the Ministry in an addendum to the advice request dated 20
June 2019 asks that specific attention be given to the objective of realistic revenues in light of the postmerger market structure with three similar-sized incumbent providers.

2.1 Spectrum packaging
The proposed spectrum packaging is:

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DotEcon. Recommended auction model for the award of 700, 1400 and 2100 MHz spectrum, June 2019.

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6 lots of 2x5 MHz at 700 MHz
8 lots of 5 MHz at 1400 MHz
12 lots of 2x5 MHz at 2100 MHz
This packaging is consistent with common practice in nearly all markets. Moreover, it facilitates
substitution across bands, which is consistent with the efficiency and simplicity objectives. It also works
well with the competition safeguard, which we discus next. We agree that this packaging is best.

2.2 Competition safeguard
The Dutch competition authority ACM has recommended the following long-term spectrum caps to
prevent excessive concentration of spectrum:
•

Overall cap: A 40% cap on mobile communications spectrum, including 700, 800, 900, 1400, 1800,
2100, and 2600 MHz as well as other frequency bands for mobile communication such as 3.5 GHz.

•

Sub-1 GHz cap: A 40% cap on low-band spectrum—all spectrum below 1 GHz—designated for
mobile communications (700, 800, and 900 MHz), rounded up to the nearest multiple of 10 MHz.

The recommended auction model must work well with this competition safeguard. This is not a problem,
as we explain below.
Given the existing spectrum holdings and the proposed spectrum award, the spectrum caps would imply
the following limits on the bidding of incumbent carriers:
•

KPN and Vodafone each can win at most 2x20 MHz (4 lots) at 700 MHz

•

T-Mobile can win at most 2x15 MHz (3 lots) at 700 MHz

•

KPN can win at most 140 MHz in the auction overall

•

Vodafone can win at most 125 MHz in the auction overall

•

T-Mobile can win at most 80 MHz in the auction overall

Spectrum caps prevent excessive concentration of spectrum. They are intended to promote competition
in the downstream market for mobile services by limiting the holdings of any one provider. The caps are
not a device to promote competition in the auction. Indeed, in this auction, there is a risk of tacit collusion
and a low-price outcome, the most likely of which is an equal split of the 700 MHz spectrum (2 lots each)
and 2100 MHz spectrum (4 lots each). One concern is that spectrum caps may facilitate tacit collusion by
preventing bidders from bidding for larger quantities. The recommended spectrum cap, however, still lets
the incumbents, especially KPN and Vodafone, to bid aggressively for spectrum. Competition among
carriers will almost surely prevent extreme outcomes where one or two bidders dominate the auction.
Thus, we anticipate that the competition safeguard is unlikely to have much impact in the auction and is
unlikely to facilitate tacit collusion.

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2.3 Preferences
Carriers provide service with a portfolio of spectrum. Low-band spectrum is especially useful in providing
coverage, whereas mid-band and high-band spectrum is better suited for capacity. The incumbent carriers
all have substantial holdings of low-band and mid-band spectrum. Thus, it is natural to assume that this
spectrum award is primarily about incremental capacity. From this perspective, we would expect
complementarities to be weak across bands. Indeed, the most likely complementarity may come from
improved spectral efficiencies in moving from a single lot to two lots of 2x5 MHz, but even this potential
synergy appears not to be large.
Within band differences among the lots appear to be minor. Lots are nearly perfect substitutes within a
band, although there is a preference for contiguous lots.
Thus, it is important that the auction handle substitutes well. Handling complements is less important in
this setting. We agree with DotEcon on this point.

3 Recommendations
With this background, we can identify design features that will best meet the Ministry objectives. For the
most part, we arrive at recommendations that are consistent with DotEcon’s recommendations.

3.1 Generic lots
The spectrum award is ideally suited to use generic lots within each band. This greatly simplifies the
auction. It improves substitution as the lots in a band become perfect substitutes. This strengthens
competition and guarantees the award of contiguous spectrum, which improves efficiency—the primary
Ministry objective. There is a long record of success with generic lots in settings like this. No party has
suggested that the lots within the same band have significantly different values. The decision to use
generic lots is an easy one. We agree with DotEcon on this point.

3.2 Assignment stage
An auction with generic lots requires an assignment stage to determine specific frequency assignments.
This is readily accomplished with a single-round sealed-bid auction with second-pricing. Within each band,
winners only have a few options, so it is an easy matter for bidders to assess the relatively minor value
differences among options. With three winners, each winner has at most four options in a band. 3 The
recommended version of second-pricing—Vickrey-nearest core pricing—provides good incentives for
truthful bidding, which supports the efficiency objective. There is a long record of success with this
approach. It is used almost universally. Because there are potential value interdependencies between the
specific assignments that a bidder obtains in the 700 MHz and the 1400 MHz band resulting from passive
With three winners, there are 3! = 3 x 2 x 1 = 6 different frequency assignments. However, a winner will have at
most 4 options, since the low option and the high option each correspond to two frequency assignments, which are
identical for the winner. That is, if the winners are A, B, C, there are six distinct orderings of A, B, C, but ABC and ACB
are equivalent for A, and similarly BCA and CBA are equivalent for A. If B and C win the same quantity, then A has
only three options, since BAC and CAB become equivalent in this case.
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intermodulation issues, DotEcon proposes to collect assignment bids for assignments in the 2100 MHz
band, and for combinations of assignments in the 700/1400 MHz bands. This makes sense. We agree with
DotEcon on the assignment stage.

3.3 Ascending auction
In contrast to the assignment stage, the primary auction should be an ascending auction. In the primary
auction there are an exponential number of possible assignments. It is unrealistic to expect bidders to
fully consider and express all these possibilities as would be required in a sealed-bid design. Rather, an
ascending auction provides valuable outcome discover about prices and likely assignments, which enables
the bidder to focus valuation efforts and better express preferences as the auction proceeds. This
improves auction efficiency. This is the primary reason ascending auctions are used in this setting. Sealedbid auctions would involve too much guesswork and too little bid expression, which would damage
efficiency.

3.4 Clock or SMRA-Clock Hybrid
One of the more difficult decisions is whether to use a combinatorial auction in which bidders bid on
packages of items. A combinatorial auction is desirable when complementarities are large. Then bidders
can bid for synergistic packages and not be exposed to aggregation risk. However, we believe that
complementarities are weak in this setting. Thus, the added complexity of a combinatorial auction is not
warranted. DotEcon arrived at the same conclusion.
There are two ascending auctions well-suited for a multi-band auction with generic lots: the clock auction
(CA+ in the DotEcon report) and the SMRA-clock hybrid. In both auctions, bidders express demand for lots
in each band. Prices increase when there is excess demand. The key difference between the two formats
is in the clock auction there is no notion of standing high bidder; whereas, in the SMRA-clock hybrid in
each round standing high bidders are determined, as in an SMRA, and each bidder is informed on which
lots the bidder is standing high bidder. Both formats have been used successfully in prior spectrum
auctions. In both cases, the version we are considering prevents changes in demand that would lead to
excess supply and the possibility of unsold lots. For the clock auction, this means that reductions in
demand are only accepted to the point where demand equals supply. For the hybrid auction, it means no
withdrawals—a standing high bidder is stuck until bumped by another bid.
DotEcon argues that the SMRA-clock hybrid is the preferred choice in this setting (section 3.3). DotEcon
argues that informing bidders about standing high bidder status helps bidders accomplish substitution
across bands. For example, when a standing high bidder is bumped on two lots in a band, the bidder knows
that it can switch that demand to another band or reduce demand. In the clock auction, the bidder can
ask for a switch or a reduction, but the switch or reduction may not be accepted because it would create
excess supply.
We argue that having this high-bidder information does not eliminate substitution risk. Suppose the
bidder wants to switch his demand of 2 lots from band A to B. Suppose the bidder is bumped on 1 lot on
band A and therefore is standing high bidder on 1 lot in A. What should the bidder do? The bidder cannot
switch to 2 lots on B. The bidder is left with two options, assuming he wants to maintain his eligibility. He
can rebid on A, even though B is preferred, or he can bid 1 lot on B, hoping that he will be able to switch
the second A lot in a future round. Both options involve substitution risk.
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DotEcon also argues that the hybrid form avoids the risk of price overshoot and unsold lots that is inherent
to clock auctions. We would however argue that in clock auctions, unsold lots are easily avoided with the
rule above that does not accept bids that would create excess supply. Price overshoot is eliminated by
letting bidders name the price point of the change in demand. Both rules are commonly used in clock
auction implementations, as in recent auctions in the US and Australia.
The clock auction allows more direct expression of demand. Changes in demand can be expressed at any
price between the prior posted price and the current clock price. In the SMRA-clock hybrid, these changes
in demand cannot be expressed for standing high bids. The clock auction has more flexible bid expression;
whereas, the hybrid approach has more certainty about whether changes in demand will be accepted.
The two approaches become more similar with small bid increments.
The case for the clock auction version is best seen in a single-band auction. Then it seems clear that the
clock auction implementation is superior to the hybrid. The clock auction is simpler. The bidder expresses
demand at the starting price and then names the price points at which demand reduces. This continues
until the price where supply and demand balance is reached. By contrast, the hybrid implementation
progresses more slower when there is little excess demand and may end with price overshoot–excess
demand at the award price and excess supply at the final round price. The auctioneer can limit this
inefficiency with a smaller bid increment, but then the hybrid auction takes even longer.
Thus, in a multiband auction where linkages between bands are sufficiently weak, the clock auction should
remain the superior choice. It is simpler and allows improved pricing with intra-round bids. However, if
linkages between bands are stronger, then it is unclear whether the clock or hybrid design should be
preferred.
Procedurally, the hybrid approach does have one advantage. Since the standing high bids remain, bidders
only need to submit bids for quantity that was bumped in the prior round, rather than full demands. This
may simplify bidding. However, in an auction with three products this is not a significant advantage.
Our conclusion is that either the clock or hybrid formats will work well in this setting. Both formats have
advantages. Both have been used successfully in a variety of recent spectrum auctions. For example, the
clock auction has been successfully used in recent auctions in the U.S., Canada, Australia, and Singapore.
We find the absence of standing high bidders in a clock auction to be an advantage as it treats all bidders
symmetrically and allows a more direct expression of demand. DotEcon prefers identifying standing high
bidders (and the resulting asymmetric treatment of bidders), since it reduces uncertainty about whether
a switch to another band will be processed. Based on our successful experience with clock auctions in
many countries and our belief that linkages across bands are not too great, we favor the clock auction in
this setting. We nonetheless conclude that the clock and clock hybrid are quite similar. Both should
perform well with respect to the Ministry’s objectives.

3.5 Activity rule
With the proposed spectrum packaging, the activity rule choice is easy. Use an eligibility point rule and
assign 2 eligibility points to each 2x5MHz lot and 1 eligibility point to each 1x5MHz lot. A bidder’s total
demand in MHz can stay the same or decrease as prices rise. This is the initial proposal of DotEcon. We
agree this is best.

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An alternative would be to base eligibility points on relative expected value. Higher-valued bands would
have proportionally higher eligibility points. However, given the uncertainty in relative values and the fact
that the three bands are broadly comparable, we favor the simpler rule, which eases substitution across
bands.
DotEcon also suggests the possibility that substitutability across bands may be with respect to downlink
capacity. Then 1 lot at 1400 MHz would substitute with 1 lot at 700 MHz, rather than 2 for 1. We suspect
that substitution is more apt to happen between the two paired bands and that the linkage with the
unpaired band to be weak. Moreover, given price expectations from prior auctions, basing eligibility points
on downlink capacity would give bidders an easy means of hiding demand for 700 MHz with bids for 1400
MHz. For this reason alone, we recommend rejecting this downlink-based alternative.
Activity rules sometimes impose a weaker activity requirement, less than 100% of current eligibility, early
in the auction, and then raise this requirement later in the auction. This is especially useful when spectrum
is auctioned on a regional basis, rather than nationwide. Given the use of nationwide lots of equal size in
each band, we believe that there is no need for a weaker activity requirement early in the auction. We
agree with DotEcon on this point.

3.6 Bid withdrawal
The SMRA format often allows a limited number of bid withdrawals. This is intended to let a bidder back
out of a failed aggregation of spectrum lots. For example, a bidder may want two lots or none. The bidder
may get stuck as the standing high bidder on one lot and find the price too high to continue to bid for two.
The bidder could then withdraw its standing high bid.
Experience has shown that withdrawals are used for various gaming purposes beyond the intended
purpose. Given that we expect synergies to be small and manageable within the context of the proposed
auction design, it seems prudent to not allow bid withdrawals.
If synergies were thought to be important, then a preferred design would be a simple clock auction that
allows reductions in demand that create excess supply. Unsold lots are then sold in a second stage in
advance of the assignment stage. The simple clock auction lets bidders express preferences for packages
of lots in response to linear prices. Both exposure risk and substitution risk are eliminated. The downside
is that some lots may go unsold as a result of multi-lot reductions in demand. Having a second stage for
unsold lots in advance of the assignment stage mitigates the problem of unsold lots. The second stage
must be designed carefully to mitigate strategic behavior in the first stage. For example, to discourage
price driving strategies one can forbid the bidder that created the excess supply with the multi-lot
reduction at the clearing price from bidding for the product in the second stage.
Simple clock auctions have been used successfully for many years. They work especially well in situations
where auctions are conducted periodically. Then any unsold quantity can be carried forward to the next
auction.

3.7 Minimum requirements
The most common synergy is a minimum requirement for lots in a band. For example, a business plan may
require that the bidder wins at least two lots in a band. Some auctions allow the bidder to specify
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minimum requirements before the auction starts. During the auction the bidder then can reduce demand
from the minimum requirement to zero without fear of winning some of what is needed. This creates the
possibility of unsold lots. However, the unsold lots can be sold in a single stage in advance of the
assignment stage.
Although there are several auctions that allowed bidders to specify minimum requirements in this way,
the actual use of the minimum requirements by bidders has been rare. We agree with DotEcon and
recommend against the use of minimum requirements here. They would add complexity without much
benefit in this setting.

3.8 Waivers
The SMRA often includes a limited number of waivers from the activity rule. When a waiver is applied, the
bidder’s eligibility is not reduced, despite failing to satisfy the activity requirement. This gives the bidder
a round to reflect on new information before committing to a course of action. It also can be applied
automatically in instances where a bidder fails to bid for whatever reason.
DotEcon argues that waivers may help a bidder overcome a switching impediment. For example, a bidder
wanting to switch two lots from one band to another, who is bumped off a single lot, can use the waiver
to see if he is bumped off his second lot in the next round and thus free to bid on two lots in the other
band. We are skeptical that such a use would be effective and important in this setting where synergies
are weak.
We recommend either no waivers or a small number, such as 1 or 2. We think the chief benefit is providing
insurance that eligibility will not be lost in the unlikely event that the bidder fails to submit a bid in a
round.

3.9 Starting prices
Starting prices can play an important role in the auction. In competitive settings, it is best to err on the
low side. Competition will push prices up to competitive and efficient levels. However, in settings where
bidding may be limited due to low participation—as seems likely here—it is advisable to have higher
starting prices that assure realistic revenues and reduce the incentive for bidders to coordinate on a lowprice outcome, which harms both the efficiency and revenue objectives. That said, the worst outcome is
setting starting prices so high that lots go unsold. One advantage of lower starting prices is they may
encourage greater participation from potential new entrants. Starting prices should be selected with care.
DotEcon only provides a limited discussion of starting prices in the draft recommendation.

3.10 Information policy
We agree with DotEcon that the preferred information policy is to reveal aggregate demand by band at
the end of each round, but not the individual bids. Revealing individual bids enables collusive strategies
that are apt to harm both efficiency and revenues. There is no countervailing benefit to the release of
individual bids during the auction.
One could reveal even less information, for example, reveal only total demand across all bands, but we
believe that knowing the demand by band is helpful to desirable outcome discovery that will improve
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bidding and auction efficiency. The recommended information policy—revealing demand by band at the
end of each round—is our preferred choice in all the clock-based auction models: SMRA-clock hybrid,
clock (CA+), and simple clock.
One motivation for not revealing information about excess demand by band is the desire to limit potential
tacit collusion. If only the three incumbents bid, the bidders may attempt to coordinate on a low-price
equilibrium in which each reduces demand to an equal share of the available spectrum. However, we do
not see why revealing aggregate demand by band would increase this possibility. Coordination on a lowprice equilibrium would seem to be equally effective whether demand is revealed or not.
After the auction, we prefer that all bids be revealed in the interest of transparency. We agree with
DotEcon on this point.

4 Conclusion
For the most part, we agree with DotEcon’s recommendations on auction rules for the award of 700, 1400,
and 2100 MHz spectrum. The analysis is broadly consistent with our understanding of the problem, the
setting, and the Ministry’s objectives. The main point of disagreement is DotEcon’s favoring of the SMRAclock hybrid, where we favor a clock auction that avoids standing high bids. Nonetheless, the two formats
are quite similar. Both are apt to perform well in this setting with respect to the Ministry’s objective.
Our biggest concern is the potential for tacit collusion. Absent a credible new entrant, incumbents may
cooperate on a low-price outcome. With the recommended design, the best and perhaps only defense
against tacit collusion is setting high starting prices that guarantee realistic revenues.
The advice of DotEcon is the result of careful consideration of the relevant factors that go into advice on
the choice of auction format. The advice of DotEcon is sufficiently motivated.

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