Home EV Chargers AI Visibility Ranking Trends - November 2026

Tracking how AI platforms recommend home ev chargers ai visibility ranking trends. Updated monthly since April 2026.

Mark Huntley, J.D.
By Mark Huntley, J.D.Growth Strategist & AI Discovery Analyst
16 minutes read
Browse 1 archived editions

Answer capsule

The November 2026 Home EV Chargers benchmark compares 9 companies across 457 AI answers that met its inclusion rules. ChargePoint Home (ChargePoint Holdings) leads with 334 recommendations (73.09% of answers). At least one tracked company was recommended in 367 answers; some answers recommended several companies.

The rankings distinguish being mentioned from receiving an affirmative recommendation, then examine placement and the wording used about each company. Earlier monthly results show how counts and rates changed, with each month using its own answer total. These results describe the answers reviewed, not product quality or customer satisfaction. Differences between monthly samples limit comparisons and do not establish why a result changed.

For the strategic interpretation of this benchmark, read CiteWorks Studio's analysis of How AI Search Is Recommending Home EV Chargers

Industry leaderboard

Questions This Section Answers

  • How do Home EV Chargers rank by recorded AI recommendations in November 2026?

Rank

Company

Recommendations

Recommendation rate

Mention rate

Top 3 rate

#1 rate

Net sentiment

1

ChargePoint Home (ChargePoint Holdings)

334

73.09%

91.25%

65.65%

26.26%

0.82

2

Tesla Wall Connector (Tesla, Inc.)

309

67.61%

93.87%

65.21%

35.45%

0.73

3

Emporia EV Charger (Emporia Energy)

257

56.24%

67.83%

49.02%

13.35%

0.85

4

Grizzl-E (United Chargers Inc.)

228

49.89%

56.24%

17.29%

1.53%

0.89

5

Autel MaxiCharger (Autel Energy)

93

20.35%

22.98%

9.19%

0.88%

0.90

6

Wallbox Pulsar Plus

61

13.35%

19.69%

6.78%

0.66%

0.68

7

Lectron

57

12.47%

18.60%

7.22%

0.88%

0.69

8

Enphase IQ (Enphase Energy)

4

0.88%

2.84%

0.66%

0.22%

0.31

9

Siemens VersiCharge (Siemens AG)

2

0.44%

0.66%

0.44%

0.22%

0.67

The leaderboard orders companies by how many answers affirmatively recommended them, so it measures recorded endorsement rather than overall presence. A company can appear often without being recommended, and recommendation counts can tie even when mention totals differ. Ties reflect equal recommendation counts, not shared wording or placement.

Placement is a further subset: first-place results sit inside shortlist placements, which sit inside recommendations. Reading the columns separately avoids treating a strong position as extra volume. The ranking describes these AI answers only, not sales, market share or customer preference.

Key findings

Tracked-company answer coverage

Questions This Section Answers

  • How often did the November 2026 Home EV Chargers answer sample recommend any tracked company?

Answer-level result

Qualified answers

Share of qualified answers

At least one tracked company mentioned

457

100.00%

At least one tracked company recommended

367

80.31%

No tracked company recommended

90

19.69%

Multiple tracked companies recommended

355

77.68%

367 distinct answers recommended at least one tracked company. Counting each company recommendation separately gives 1345, because an answer can recommend several companies. Answers with no tracked recommendation may still have recommended companies outside this comparison.

Nearly every qualified answer mentioned at least one tracked company, and most recommended one. Multiple recommendations within a single answer were common, which is why company-level recommendation totals exceed the number of answers containing any recommendation. Overlap is expected and does not indicate dominance.

A meaningful minority of answers recommended no tracked company. Those answers may still have named companies outside this comparison, so the coverage figures describe the tracked set rather than the whole answer space.

Reach and affirmative recommendation

ChargePoint Home (ChargePoint Holdings) ranks 1 by recommendation count. Mentions: 417 (91.25%); recommendations: 334 (73.09%). Top 3 placements: 300 (65.65%); first-place placements: 120 (26.26%).

Wording about the company: 340 positive, 77 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 80.1%. The net framing score was 0.82 (defined in Methodology).

83 mentions had no recorded recommendation. Of recorded recommendations, 89.82% were Top 3 and 35.93% were first-place.

ChargePoint Home leads on recommendation count, but its mention total is slightly below Tesla Wall Connector's. That gap shows why presence and endorsement answer different questions: an answer can name a company without affirming it. The recommendation-to-mention ratio summarizes how often a mention carried an endorsement in these answers.

A high ratio on a large base is a stable reading; the same ratio on a small base is less informative. Neither ratio measures customer behavior or product merit.

Recommendation order and placement

Company

Mentions

Recommendation-to-mention ratio

Top 3 / #1 counts

Positive / neutral / negative mentions

ChargePoint Home (ChargePoint Holdings)

417

80.1%

300 / 120

340 / 77 / 0

Tesla Wall Connector (Tesla, Inc.)

429

72.0%

298 / 162

315 / 114 / 0

Emporia EV Charger (Emporia Energy)

310

82.9%

224 / 61

262 / 48 / 0

Grizzl-E (United Chargers Inc.)

257

88.7%

79 / 7

228 / 29 / 0

Autel MaxiCharger (Autel Energy)

105

88.6%

42 / 4

94 / 11 / 0

Wallbox Pulsar Plus

90

67.8%

31 / 3

61 / 29 / 0

Lectron

85

67.1%

33 / 4

59 / 26 / 0

Enphase IQ (Enphase Energy)

13

30.8%

3 / 1

4 / 9 / 0

Siemens VersiCharge (Siemens AG)

3

66.7%

2 / 1

2 / 1 / 0

Placement columns describe where recommendations landed in an answer's ordering, not additional recommendations. Shortlist and first-place counts are nested within the recommendation total, so they should not be summed with it. Companies with similar recommendation counts can differ sharply in how often they appear near the top.

Ratios computed within recommendations are sensitive to small bases, particularly for companies with few recorded recommendations. Those figures are best read alongside the raw counts rather than in isolation.

Classified framing in context

Company

Positive

Neutral

Negative

ChargePoint Home (ChargePoint Holdings)

340

77

0

Tesla Wall Connector (Tesla, Inc.)

315

114

0

Emporia EV Charger (Emporia Energy)

262

48

0

Grizzl-E (United Chargers Inc.)

228

29

0

Autel MaxiCharger (Autel Energy)

94

11

0

Wallbox Pulsar Plus

61

29

0

Lectron

59

26

0

Enphase IQ (Enphase Energy)

4

9

0

Siemens VersiCharge (Siemens AG)

2

1

0

Framing classifies the wording surrounding each mention as positive, neutral or negative. No tracked company recorded negative wording in this sample, so differences come from the balance of positive and neutral language. A neutral mention is still a mention; it simply lacks affirmative framing.

Framing is not customer sentiment, reputation or a quality judgment, and it does not explain why recommendations occurred. The net framing score compresses this balance into a single value and should be read with the underlying counts.

Company results in detail

ChargePoint Home (ChargePoint Holdings)

Questions This Section Answers

  • What do the November 2026 AI answer results show about ChargePoint Home (ChargePoint Holdings) mentions, recommendations and placement?

ChargePoint Home (ChargePoint Holdings) ranks 1 by recommendation count. Mentions: 417 (91.25%); recommendations: 334 (73.09%). Top 3 placements: 300 (65.65%); first-place placements: 120 (26.26%).

Wording about the company: 340 positive, 77 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 80.1%. The net framing score was 0.82 (defined in Methodology).

83 mentions had no recorded recommendation. Of recorded recommendations, 89.82% were Top 3 and 35.93% were first-place.

From October 2026 to November 2026, ChargePoint Home (ChargePoint Holdings)'s mention count rose from 0 to 417, while its recommendation count rose from 0 to 334. The recommendation rate was 0.00% and 73.09% respectively.

ChargePoint Home tops the recommendation ranking while appearing in slightly fewer answers than Tesla Wall Connector, so its lead rests on endorsement frequency rather than raw presence. Most of its mentions carried a recommendation, and its placements skew toward the upper part of answers.

Wording was overwhelmingly positive with no negative mentions recorded. The prior month recorded no recommendations for this company, so the November figures stand as a separate sample rather than a demonstrated recovery.

Tesla Wall Connector (Tesla, Inc.)

Questions This Section Answers

Tesla Wall Connector (Tesla, Inc.) ranks 2 by recommendation count. Mentions: 429 (93.87%); recommendations: 309 (67.61%). Top 3 placements: 298 (65.21%); first-place placements: 162 (35.45%).

Wording about the company: 315 positive, 114 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 72.0%. The net framing score was 0.73 (defined in Methodology).

120 mentions had no recorded recommendation. Of recorded recommendations, 96.44% were Top 3 and 52.43% were first-place.

From October 2026 to November 2026, Tesla Wall Connector (Tesla, Inc.)'s mention count rose from 0 to 429, while its recommendation count rose from 0 to 309. The recommendation rate was 0.00% and 67.61% respectively.

Tesla Wall Connector recorded the most mentions of any tracked company but ranked second on recommendations, meaning a larger share of its appearances went unendorsed. Among the recommendations it did receive, a comparatively high share landed in first place, giving it a distinctive placement profile.

Framing was mostly positive with a substantial neutral remainder. The October sample recorded no recommendations, so the month-to-month change reflects different answer samples rather than an established trend.

Emporia EV Charger (Emporia Energy)

Questions This Section Answers

Emporia EV Charger (Emporia Energy) ranks 3 by recommendation count. Mentions: 310 (67.83%); recommendations: 257 (56.24%). Top 3 placements: 224 (49.02%); first-place placements: 61 (13.35%).

Wording about the company: 262 positive, 48 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 82.9%. The net framing score was 0.85 (defined in Methodology).

53 mentions had no recorded recommendation. Of recorded recommendations, 87.16% were Top 3 and 23.74% were first-place.

From October 2026 to November 2026, Emporia EV Charger (Emporia Energy)'s mention count rose from 0 to 310, while its recommendation count rose from 0 to 257. The recommendation rate was 0.00% and 56.24% respectively.

Emporia EV Charger holds third place with a recommendation-to-mention ratio above both companies ahead of it, indicating that when it appeared, endorsement usually followed. Its shortlist placements are frequent, but first-place finishes are comparatively rare, so its strength lies in being recommended rather than ranked at the top.

Framing was largely positive with no negative mentions. The prior month recorded no recommendations, and the comparison should be read as separate samples.

Grizzl-E (United Chargers Inc.)

Questions This Section Answers

Grizzl-E (United Chargers Inc.) ranks 4 by recommendation count. Mentions: 257 (56.24%); recommendations: 228 (49.89%). Top 3 placements: 79 (17.29%); first-place placements: 7 (1.53%).

Wording about the company: 228 positive, 29 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 88.7%. The net framing score was 0.89 (defined in Methodology).

29 mentions had no recorded recommendation. Of recorded recommendations, 34.65% were Top 3 and 3.07% were first-place.

From October 2026 to November 2026, Grizzl-E (United Chargers Inc.)'s mention count rose from 0 to 257, while its recommendation count rose from 0 to 228. The recommendation rate was 0.00% and 49.89% respectively.

Grizzl-E shows one of the highest recommendation-to-mention ratios in the set, meaning most of its appearances carried an affirmative endorsement. Its placement profile is markedly different: shortlist and especially first-place finishes are uncommon relative to its recommendation volume, so it is endorsed more often than it is ranked highly.

Framing was almost entirely positive. The October sample recorded no recommendations, so no continuity can be inferred across months.

Autel MaxiCharger (Autel Energy)

Questions This Section Answers

Autel MaxiCharger (Autel Energy) ranks 5 by recommendation count. Mentions: 105 (22.98%); recommendations: 93 (20.35%). Top 3 placements: 42 (9.19%); first-place placements: 4 (0.88%).

Wording about the company: 94 positive, 11 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 88.6%. The net framing score was 0.90 (defined in Methodology).

12 mentions had no recorded recommendation. Of recorded recommendations, 45.16% were Top 3 and 4.30% were first-place.

From October 2026 to November 2026, Autel MaxiCharger (Autel Energy)'s mention count rose from 0 to 105, while its recommendation count rose from 0 to 93. The recommendation rate was 0.00% and 20.35% respectively.

Autel MaxiCharger reaches fifth place on a smaller mention base than the leaders, with a recommendation-to-mention ratio comparable to Grizzl-E's. Its placements are modest: shortlist appearances occur but first-place finishes are rare, so endorsement frequency outpaces positional prominence.

Framing was predominantly positive with a small neutral share and no negative mentions. The prior month recorded no recommendations, and the change reflects a different answer sample.

Wallbox Pulsar Plus

Questions This Section Answers

  • What do the November 2026 AI answer results show about Wallbox Pulsar Plus mentions, recommendations and placement?

Wallbox Pulsar Plus ranks 6 by recommendation count. Mentions: 90 (19.69%); recommendations: 61 (13.35%). Top 3 placements: 31 (6.78%); first-place placements: 3 (0.66%).

Wording about the company: 61 positive, 29 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 67.8%. The net framing score was 0.68 (defined in Methodology).

29 mentions had no recorded recommendation. Of recorded recommendations, 50.82% were Top 3 and 4.92% were first-place.

From October 2026 to November 2026, Wallbox Pulsar Plus' mention count fell from 114 to 90, while its recommendation count fell from 83 to 61. The recommendation rate was 15.40% and 13.35% respectively.

Wallbox Pulsar Plus recorded fewer mentions and recommendations than in the prior month, and its recommendation rate also eased slightly. The counts and the rate moved in the same direction, but the smaller November answer total means the two months are separate samples and the change cannot be attributed to any cause.

Its recommendation-to-mention ratio is moderate, and first-place finishes are rare. Framing was mostly positive with a sizeable neutral share.

Lectron

Questions This Section Answers

  • What do the November 2026 AI answer results show about Lectron mentions, recommendations and placement?

Lectron ranks 7 by recommendation count. Mentions: 85 (18.60%); recommendations: 57 (12.47%). Top 3 placements: 33 (7.22%); first-place placements: 4 (0.88%).

Wording about the company: 59 positive, 26 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 67.1%. The net framing score was 0.69 (defined in Methodology).

28 mentions had no recorded recommendation. Of recorded recommendations, 57.89% were Top 3 and 7.02% were first-place.

From October 2026 to November 2026, Lectron's mention count fell from 126 to 85, while its recommendation count fell from 64 to 57. The recommendation rate was 11.87% and 12.47% respectively.

Lectron's mention count fell from the prior month while its recommendation count declined by less, so its recommendation rate edged upward even as both raw counts dropped. That pattern illustrates why rates and counts can point in different directions; neither establishes a trend across separate monthly samples.

Its recommendation-to-mention ratio is moderate, with shortlist placements more common than first-place ones. Framing was mostly positive with a notable neutral share.

Enphase IQ (Enphase Energy)

Questions This Section Answers

Enphase IQ (Enphase Energy) ranks 8 by recommendation count. Mentions: 13 (2.84%); recommendations: 4 (0.88%). Top 3 placements: 3 (0.66%); first-place placements: 1 (0.22%).

Wording about the company: 4 positive, 9 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 30.8%. The net framing score was 0.31 (defined in Methodology).

9 mentions had no recorded recommendation. Of recorded recommendations, 75.00% were Top 3 and 25.00% were first-place.

From October 2026 to November 2026, Enphase IQ (Enphase Energy)'s mention count rose from 0 to 13, while its recommendation count rose from 0 to 4. The recommendation rate was 0.00% and 0.88% respectively.

Enphase IQ appears in relatively few answers, and only a minority of those mentions carried a recommendation, giving it the lowest recommendation-to-mention ratio among tracked companies. Its placement counts are correspondingly small, and the within-recommendation ratios rest on a sparse base.

Framing was more often neutral than positive, with no negative mentions. The prior month recorded no recommendations, so the November figures are a fresh sample rather than a continuation.

Siemens VersiCharge (Siemens AG)

Questions This Section Answers

Siemens VersiCharge (Siemens AG) ranks 9 by recommendation count. Mentions: 3 (0.66%); recommendations: 2 (0.44%). Top 3 placements: 2 (0.44%); first-place placements: 1 (0.22%).

Wording about the company: 2 positive, 1 neutral, 0 negative mentions. The proportion of mentions that also included a recommendation was 66.7%. The net framing score was 0.67 (defined in Methodology).

1 mentions had no recorded recommendation. Of recorded recommendations, 100.00% were Top 3 and 50.00% were first-place.

From October 2026 to November 2026, Siemens VersiCharge (Siemens AG)'s mention count rose from 0 to 3, while its recommendation count rose from 0 to 2. The recommendation rate was 0.00% and 0.44% respectively.

Siemens VersiCharge recorded very few mentions and recommendations, placing it last on recommendation count. Its recommendation-to-mention ratio looks high, but it rests on a handful of observations and should be treated as indicative only. Placement counts are similarly sparse.

Framing was mostly positive with one neutral mention and no negatives. The prior month recorded no recommendations, and the small totals limit any comparison across months.

Earlier ranking snapshot context

Questions This Section Answers

  • How do the available Home EV Chargers snapshots from July 2026 to November 2026 differ in recommendation coverage and measurement scope?

Company

Jul 2026

Aug 2026

Sep 2026

Oct 2026

Nov 2026

ChargePoint Home (ChargePoint Holdings)

329 / 535 (61.50%)

319 / 554 (57.58%)

303 / 568 (53.35%)

0 / 539 (0.00%)

334 / 457 (73.09%)

Tesla Wall Connector (Tesla, Inc.)

301 / 535 (56.26%)

278 / 554 (50.18%)

294 / 568 (51.76%)

0 / 539 (0.00%)

309 / 457 (67.61%)

Emporia EV Charger (Emporia Energy)

246 / 535 (45.98%)

240 / 554 (43.32%)

226 / 568 (39.79%)

0 / 539 (0.00%)

257 / 457 (56.24%)

Grizzl-E (United Chargers Inc.)

199 / 535 (37.20%)

197 / 554 (35.56%)

219 / 568 (38.56%)

0 / 539 (0.00%)

228 / 457 (49.89%)

Autel MaxiCharger (Autel Energy)

66 / 535 (12.34%)

56 / 554 (10.11%)

69 / 568 (12.15%)

0 / 539 (0.00%)

93 / 457 (20.35%)

Wallbox Pulsar Plus

127 / 535 (23.74%)

89 / 554 (16.06%)

82 / 568 (14.44%)

83 / 539 (15.40%)

61 / 457 (13.35%)

Lectron

59 / 535 (11.03%)

66 / 554 (11.91%)

63 / 568 (11.09%)

64 / 539 (11.87%)

57 / 457 (12.47%)

Enphase IQ (Enphase Energy)

13 / 535 (2.43%)

9 / 554 (1.62%)

8 / 568 (1.41%)

0 / 539 (0.00%)

4 / 457 (0.88%)

Siemens VersiCharge (Siemens AG)

3 / 535 (0.56%)

4 / 554 (0.72%)

3 / 568 (0.53%)

0 / 539 (0.00%)

2 / 457 (0.44%)

Company

Jul 2026 rank

Aug 2026 rank

Sep 2026 rank

Oct 2026 rank

Nov 2026 rank

ChargePoint Home (ChargePoint Holdings)

1

1

1

3

1

Tesla Wall Connector (Tesla, Inc.)

2

2

2

3

2

Emporia EV Charger (Emporia Energy)

3

3

3

3

3

Grizzl-E (United Chargers Inc.)

4

4

4

3

4

Autel MaxiCharger (Autel Energy)

6

7

6

3

5

Wallbox Pulsar Plus

5

5

5

1

6

Lectron

7

6

7

2

7

Enphase IQ (Enphase Energy)

8

8

8

3

8

Siemens VersiCharge (Siemens AG)

9

9

9

3

9

Only months with verified results are shown. Monthly sample coverage is listed in Methodology.

Earlier months are separate samples with their own answer totals, so counts and rates are not directly comparable across columns. The October snapshot shows several companies with no recorded recommendations, which is a measured result for that sample rather than a missing observation.

Rank changes across months describe how the recorded results differed; they do not establish stability, decline or the effect of any intervention. Rates should be read alongside the answer totals that produced them.

AI recommendation trend

Observed recommendation rate (%), Jul 2026 to Nov 2026

0%20%40%60%80%Jul 2026Aug 2026Sep 2026Oct 2026Nov 2026
  • ChargePoint Home (ChargePoint Holdings)73.1%
  • Tesla Wall Connector (Tesla, Inc.)67.6%
  • Emporia EV Charger (Emporia Energy)56.2%
  • Grizzl-E (United Chargers Inc.)49.9%
  • Autel MaxiCharger (Autel Energy)20.4%
  • Wallbox Pulsar Plus13.3%
  • Lectron12.5%
  • Enphase IQ (Enphase Energy)0.9%
  • Siemens VersiCharge (Siemens AG)0.4%

What the November Rankings Show

The November results answer several distinct questions. Reach asks whether a company appeared at all; recommendation asks whether the answer affirmatively endorsed it; placement asks where that endorsement sat in the ordering; framing describes the wording around the mention. A company can be prominent on one measure and modest on another, as the differing mention and recommendation orders show.

Because recommendations nest inside mentions and placements nest inside recommendations, the columns are not additive. Ratios on small bases are less reliable than those on large ones, and framing is not customer sentiment. The figures describe the reviewed AI answers, not verified product facts or commercial outcomes.

Methodology

Questions This Section Answers

  • How were the November 2026 Home EV Chargers AI visibility measures counted, and what do they not establish?

This benchmark has partial coverage: 3 of 3 planned question categories contributed usable observations; 0 contributed none. This describes question-category coverage, not demonstrated platform outages. Findings apply to the available answer set.

The month in the title is the reporting period. The exact dates when the original AI answers were collected have not been verified.

Each company is counted at most once in each answer that meets the benchmark rules. A recommendation requires both an affirmative endorsement and positive wording. Mention, recommendation, Top 3 and first-place rates use the full benchmark answer total. Top 3 and first-place results are included within recommendations, not added to them.

The recommendation-to-mention ratio divides recommendations by mentions. It describes AI answer wording, not customer conversion. Net framing is positive minus negative mentions, divided by all mentions, on a scale from -1 to +1. It does not measure customer satisfaction or company quality.

Market: US; 9 tracked companies. AI services represented: ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity.

Research screening totals (answer observations can include repeated questions):

Screening measure

Count

Answers included in the benchmark

457

Answers marked relevant during screening

711

Answers marked reserved (screening label)

254

Answers marked irrelevant during screening

89

Captured answer observations

800

Distinct questions

537

Answer observations marked as mentioning a brand

800

The source does not provide a reader-facing definition of “reserved”; that screening label is reported without inferring a reason for exclusion. Only the included benchmark answers form the rate denominator.

One answer can mention or recommend several companies. Adding company totals would therefore count some answers more than once. The results describe the AI answers reviewed, not independently verified facts about the companies or their products.

Monthly sample coverage:

Reporting month

Answers included

AI services covered

Services

Jul 2026

535

6

ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity

Aug 2026

554

6

ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity

Sep 2026

568

6

ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity

Oct 2026

539

6

ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity

Nov 2026

457

6

ChatGPT, Copilot, Gemini, Google AI Mode, Google AI Overviews, Perplexity

The answer samples differ between months. These comparisons show how the recorded results changed; they do not establish why they changed.

These findings cover the available answer set, which had partial question-category coverage; that reflects screening coverage, not demonstrated platform outages. The reporting month labels the period, though exact collection dates were not verified. Each company is counted at most once per answer, and a recommendation requires both affirmative endorsement and positive wording.

Mention, recommendation and placement rates use the full benchmark answer total, while the recommendation-to-mention ratio uses mentions as its base. Net framing runs from negative to positive and is not a satisfaction measure. Monthly samples differ in size, so comparisons show recorded change without establishing its cause.

Archived editions

Browse earlier published research snapshots for this article. The latest edition remains at the current URL.